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authorLinus Torvalds <torvalds@linux-foundation.org>2019-01-02 09:48:13 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-01-02 09:48:13 -0800
commitd9a7fa67b4bfe6ce93ee9aab23ae2e7ca0763e84 (patch)
treeea15c22c088160107c09da1c8d380753bb0c8d21
parentf218a29c25ad8abdb961435d6b8139f462061364 (diff)
parent55b8cbe470d103b44104c64dbf89e5cad525d4e0 (diff)
downloadlinux-stericsson-d9a7fa67b4bfe6ce93ee9aab23ae2e7ca0763e84.tar.gz
Merge branch 'next-seccomp' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security
Pull seccomp updates from James Morris: - Add SECCOMP_RET_USER_NOTIF - seccomp fixes for sparse warnings and s390 build (Tycho) * 'next-seccomp' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: seccomp, s390: fix build for syscall type change seccomp: fix poor type promotion samples: add an example of seccomp user trap seccomp: add a return code to trap to userspace seccomp: switch system call argument type to void * seccomp: hoist struct seccomp_data recalculation higher
-rw-r--r--Documentation/ioctl/ioctl-number.txt1
-rw-r--r--Documentation/userspace-api/seccomp_filter.rst84
-rw-r--r--arch/s390/kernel/compat_wrapper.c2
-rw-r--r--include/linux/seccomp.h9
-rw-r--r--include/linux/syscalls.h2
-rw-r--r--include/uapi/linux/seccomp.h40
-rw-r--r--kernel/seccomp.c467
-rw-r--r--samples/seccomp/.gitignore1
-rw-r--r--samples/seccomp/Makefile7
-rw-r--r--samples/seccomp/user-trap.c375
-rw-r--r--tools/testing/selftests/seccomp/seccomp_bpf.c447
11 files changed, 1411 insertions, 24 deletions
diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
index af6f6ba1fe80..c9558146ac58 100644
--- a/Documentation/ioctl/ioctl-number.txt
+++ b/Documentation/ioctl/ioctl-number.txt
@@ -79,6 +79,7 @@ Code Seq#(hex) Include File Comments
0x1b all InfiniBand Subsystem <http://infiniband.sourceforge.net/>
0x20 all drivers/cdrom/cm206.h
0x22 all scsi/sg.h
+'!' 00-1F uapi/linux/seccomp.h
'#' 00-3F IEEE 1394 Subsystem Block for the entire subsystem
'$' 00-0F linux/perf_counter.h, linux/perf_event.h
'%' 00-0F include/uapi/linux/stm.h
diff --git a/Documentation/userspace-api/seccomp_filter.rst b/Documentation/userspace-api/seccomp_filter.rst
index 82a468bc7560..b1b846d8a094 100644
--- a/Documentation/userspace-api/seccomp_filter.rst
+++ b/Documentation/userspace-api/seccomp_filter.rst
@@ -122,6 +122,11 @@ In precedence order, they are:
Results in the lower 16-bits of the return value being passed
to userland as the errno without executing the system call.
+``SECCOMP_RET_USER_NOTIF``:
+ Results in a ``struct seccomp_notif`` message sent on the userspace
+ notification fd, if it is attached, or ``-ENOSYS`` if it is not. See below
+ on discussion of how to handle user notifications.
+
``SECCOMP_RET_TRACE``:
When returned, this value will cause the kernel to attempt to
notify a ``ptrace()``-based tracer prior to executing the system
@@ -183,6 +188,85 @@ The ``samples/seccomp/`` directory contains both an x86-specific example
and a more generic example of a higher level macro interface for BPF
program generation.
+Userspace Notification
+======================
+
+The ``SECCOMP_RET_USER_NOTIF`` return code lets seccomp filters pass a
+particular syscall to userspace to be handled. This may be useful for
+applications like container managers, which wish to intercept particular
+syscalls (``mount()``, ``finit_module()``, etc.) and change their behavior.
+
+To acquire a notification FD, use the ``SECCOMP_FILTER_FLAG_NEW_LISTENER``
+argument to the ``seccomp()`` syscall:
+
+.. code-block:: c
+
+ fd = seccomp(SECCOMP_SET_MODE_FILTER, SECCOMP_FILTER_FLAG_NEW_LISTENER, &prog);
+
+which (on success) will return a listener fd for the filter, which can then be
+passed around via ``SCM_RIGHTS`` or similar. Note that filter fds correspond to
+a particular filter, and not a particular task. So if this task then forks,
+notifications from both tasks will appear on the same filter fd. Reads and
+writes to/from a filter fd are also synchronized, so a filter fd can safely
+have many readers.
+
+The interface for a seccomp notification fd consists of two structures:
+
+.. code-block:: c
+
+ struct seccomp_notif_sizes {
+ __u16 seccomp_notif;
+ __u16 seccomp_notif_resp;
+ __u16 seccomp_data;
+ };
+
+ struct seccomp_notif {
+ __u64 id;
+ __u32 pid;
+ __u32 flags;
+ struct seccomp_data data;
+ };
+
+ struct seccomp_notif_resp {
+ __u64 id;
+ __s64 val;
+ __s32 error;
+ __u32 flags;
+ };
+
+The ``struct seccomp_notif_sizes`` structure can be used to determine the size
+of the various structures used in seccomp notifications. The size of ``struct
+seccomp_data`` may change in the future, so code should use:
+
+.. code-block:: c
+
+ struct seccomp_notif_sizes sizes;
+ seccomp(SECCOMP_GET_NOTIF_SIZES, 0, &sizes);
+
+to determine the size of the various structures to allocate. See
+samples/seccomp/user-trap.c for an example.
+
+Users can read via ``ioctl(SECCOMP_IOCTL_NOTIF_RECV)`` (or ``poll()``) on a
+seccomp notification fd to receive a ``struct seccomp_notif``, which contains
+five members: the input length of the structure, a unique-per-filter ``id``,
+the ``pid`` of the task which triggered this request (which may be 0 if the
+task is in a pid ns not visible from the listener's pid namespace), a ``flags``
+member which for now only has ``SECCOMP_NOTIF_FLAG_SIGNALED``, representing
+whether or not the notification is a result of a non-fatal signal, and the
+``data`` passed to seccomp. Userspace can then make a decision based on this
+information about what to do, and ``ioctl(SECCOMP_IOCTL_NOTIF_SEND)`` a
+response, indicating what should be returned to userspace. The ``id`` member of
+``struct seccomp_notif_resp`` should be the same ``id`` as in ``struct
+seccomp_notif``.
+
+It is worth noting that ``struct seccomp_data`` contains the values of register
+arguments to the syscall, but does not contain pointers to memory. The task's
+memory is accessible to suitably privileged traces via ``ptrace()`` or
+``/proc/pid/mem``. However, care should be taken to avoid the TOCTOU mentioned
+above in this document: all arguments being read from the tracee's memory
+should be read into the tracer's memory before any policy decisions are made.
+This allows for an atomic decision on syscall arguments.
+
Sysctls
=======
diff --git a/arch/s390/kernel/compat_wrapper.c b/arch/s390/kernel/compat_wrapper.c
index 2ce28bf0c5ec..48c4ce668244 100644
--- a/arch/s390/kernel/compat_wrapper.c
+++ b/arch/s390/kernel/compat_wrapper.c
@@ -164,7 +164,7 @@ COMPAT_SYSCALL_WRAP3(finit_module, int, fd, const char __user *, uargs, int, fla
COMPAT_SYSCALL_WRAP3(sched_setattr, pid_t, pid, struct sched_attr __user *, attr, unsigned int, flags);
COMPAT_SYSCALL_WRAP4(sched_getattr, pid_t, pid, struct sched_attr __user *, attr, unsigned int, size, unsigned int, flags);
COMPAT_SYSCALL_WRAP5(renameat2, int, olddfd, const char __user *, oldname, int, newdfd, const char __user *, newname, unsigned int, flags);
-COMPAT_SYSCALL_WRAP3(seccomp, unsigned int, op, unsigned int, flags, const char __user *, uargs)
+COMPAT_SYSCALL_WRAP3(seccomp, unsigned int, op, unsigned int, flags, void __user *, uargs)
COMPAT_SYSCALL_WRAP3(getrandom, char __user *, buf, size_t, count, unsigned int, flags)
COMPAT_SYSCALL_WRAP2(memfd_create, const char __user *, uname, unsigned int, flags)
COMPAT_SYSCALL_WRAP3(bpf, int, cmd, union bpf_attr *, attr, unsigned int, size);
diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index e5320f6c8654..84868d37b35d 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -4,9 +4,10 @@
#include <uapi/linux/seccomp.h>
-#define SECCOMP_FILTER_FLAG_MASK (SECCOMP_FILTER_FLAG_TSYNC | \
- SECCOMP_FILTER_FLAG_LOG | \
- SECCOMP_FILTER_FLAG_SPEC_ALLOW)
+#define SECCOMP_FILTER_FLAG_MASK (SECCOMP_FILTER_FLAG_TSYNC | \
+ SECCOMP_FILTER_FLAG_LOG | \
+ SECCOMP_FILTER_FLAG_SPEC_ALLOW | \
+ SECCOMP_FILTER_FLAG_NEW_LISTENER)
#ifdef CONFIG_SECCOMP
@@ -43,7 +44,7 @@ extern void secure_computing_strict(int this_syscall);
#endif
extern long prctl_get_seccomp(void);
-extern long prctl_set_seccomp(unsigned long, char __user *);
+extern long prctl_set_seccomp(unsigned long, void __user *);
static inline int seccomp_mode(struct seccomp *s)
{
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 251979d2e709..257cccba3062 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -898,7 +898,7 @@ asmlinkage long sys_renameat2(int olddfd, const char __user *oldname,
int newdfd, const char __user *newname,
unsigned int flags);
asmlinkage long sys_seccomp(unsigned int op, unsigned int flags,
- const char __user *uargs);
+ void __user *uargs);
asmlinkage long sys_getrandom(char __user *buf, size_t count,
unsigned int flags);
asmlinkage long sys_memfd_create(const char __user *uname_ptr, unsigned int flags);
diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h
index 9efc0e73d50b..90734aa5aa36 100644
--- a/include/uapi/linux/seccomp.h
+++ b/include/uapi/linux/seccomp.h
@@ -15,11 +15,13 @@
#define SECCOMP_SET_MODE_STRICT 0
#define SECCOMP_SET_MODE_FILTER 1
#define SECCOMP_GET_ACTION_AVAIL 2
+#define SECCOMP_GET_NOTIF_SIZES 3
/* Valid flags for SECCOMP_SET_MODE_FILTER */
-#define SECCOMP_FILTER_FLAG_TSYNC (1UL << 0)
-#define SECCOMP_FILTER_FLAG_LOG (1UL << 1)
-#define SECCOMP_FILTER_FLAG_SPEC_ALLOW (1UL << 2)
+#define SECCOMP_FILTER_FLAG_TSYNC (1UL << 0)
+#define SECCOMP_FILTER_FLAG_LOG (1UL << 1)
+#define SECCOMP_FILTER_FLAG_SPEC_ALLOW (1UL << 2)
+#define SECCOMP_FILTER_FLAG_NEW_LISTENER (1UL << 3)
/*
* All BPF programs must return a 32-bit value.
@@ -35,6 +37,7 @@
#define SECCOMP_RET_KILL SECCOMP_RET_KILL_THREAD
#define SECCOMP_RET_TRAP 0x00030000U /* disallow and force a SIGSYS */
#define SECCOMP_RET_ERRNO 0x00050000U /* returns an errno */
+#define SECCOMP_RET_USER_NOTIF 0x7fc00000U /* notifies userspace */
#define SECCOMP_RET_TRACE 0x7ff00000U /* pass to a tracer or disallow */
#define SECCOMP_RET_LOG 0x7ffc0000U /* allow after logging */
#define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */
@@ -60,4 +63,35 @@ struct seccomp_data {
__u64 args[6];
};
+struct seccomp_notif_sizes {
+ __u16 seccomp_notif;
+ __u16 seccomp_notif_resp;
+ __u16 seccomp_data;
+};
+
+struct seccomp_notif {
+ __u64 id;
+ __u32 pid;
+ __u32 flags;
+ struct seccomp_data data;
+};
+
+struct seccomp_notif_resp {
+ __u64 id;
+ __s64 val;
+ __s32 error;
+ __u32 flags;
+};
+
+#define SECCOMP_IOC_MAGIC '!'
+#define SECCOMP_IO(nr) _IO(SECCOMP_IOC_MAGIC, nr)
+#define SECCOMP_IOR(nr, type) _IOR(SECCOMP_IOC_MAGIC, nr, type)
+#define SECCOMP_IOW(nr, type) _IOW(SECCOMP_IOC_MAGIC, nr, type)
+#define SECCOMP_IOWR(nr, type) _IOWR(SECCOMP_IOC_MAGIC, nr, type)
+
+/* Flags for seccomp notification fd ioctl. */
+#define SECCOMP_IOCTL_NOTIF_RECV SECCOMP_IOWR(0, struct seccomp_notif)
+#define SECCOMP_IOCTL_NOTIF_SEND SECCOMP_IOWR(1, \
+ struct seccomp_notif_resp)
+#define SECCOMP_IOCTL_NOTIF_ID_VALID SECCOMP_IOR(2, __u64)
#endif /* _UAPI_LINUX_SECCOMP_H */
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index f2ae2324c232..d7f538847b84 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -33,12 +33,74 @@
#endif
#ifdef CONFIG_SECCOMP_FILTER
+#include <linux/file.h>
#include <linux/filter.h>
#include <linux/pid.h>
#include <linux/ptrace.h>
#include <linux/security.h>
#include <linux/tracehook.h>
#include <linux/uaccess.h>
+#include <linux/anon_inodes.h>
+
+enum notify_state {
+ SECCOMP_NOTIFY_INIT,
+ SECCOMP_NOTIFY_SENT,
+ SECCOMP_NOTIFY_REPLIED,
+};
+
+struct seccomp_knotif {
+ /* The struct pid of the task whose filter triggered the notification */
+ struct task_struct *task;
+
+ /* The "cookie" for this request; this is unique for this filter. */
+ u64 id;
+
+ /*
+ * The seccomp data. This pointer is valid the entire time this
+ * notification is active, since it comes from __seccomp_filter which
+ * eclipses the entire lifecycle here.
+ */
+ const struct seccomp_data *data;
+
+ /*
+ * Notification states. When SECCOMP_RET_USER_NOTIF is returned, a
+ * struct seccomp_knotif is created and starts out in INIT. Once the
+ * handler reads the notification off of an FD, it transitions to SENT.
+ * If a signal is received the state transitions back to INIT and
+ * another message is sent. When the userspace handler replies, state
+ * transitions to REPLIED.
+ */
+ enum notify_state state;
+
+ /* The return values, only valid when in SECCOMP_NOTIFY_REPLIED */
+ int error;
+ long val;
+
+ /* Signals when this has entered SECCOMP_NOTIFY_REPLIED */
+ struct completion ready;
+
+ struct list_head list;
+};
+
+/**
+ * struct notification - container for seccomp userspace notifications. Since
+ * most seccomp filters will not have notification listeners attached and this
+ * structure is fairly large, we store the notification-specific stuff in a
+ * separate structure.
+ *
+ * @request: A semaphore that users of this notification can wait on for
+ * changes. Actual reads and writes are still controlled with
+ * filter->notify_lock.
+ * @next_id: The id of the next request.
+ * @notifications: A list of struct seccomp_knotif elements.
+ * @wqh: A wait queue for poll.
+ */
+struct notification {
+ struct semaphore request;
+ u64 next_id;
+ struct list_head notifications;
+ wait_queue_head_t wqh;
+};
/**
* struct seccomp_filter - container for seccomp BPF programs
@@ -50,6 +112,8 @@
* @log: true if all actions except for SECCOMP_RET_ALLOW should be logged
* @prev: points to a previously installed, or inherited, filter
* @prog: the BPF program to evaluate
+ * @notif: the struct that holds all notification related information
+ * @notify_lock: A lock for all notification-related accesses.
*
* seccomp_filter objects are organized in a tree linked via the @prev
* pointer. For any task, it appears to be a singly-linked list starting
@@ -66,6 +130,8 @@ struct seccomp_filter {
bool log;
struct seccomp_filter *prev;
struct bpf_prog *prog;
+ struct notification *notif;
+ struct mutex notify_lock;
};
/* Limit any path through the tree to 256KB worth of instructions. */
@@ -188,7 +254,6 @@ static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
static u32 seccomp_run_filters(const struct seccomp_data *sd,
struct seccomp_filter **match)
{
- struct seccomp_data sd_local;
u32 ret = SECCOMP_RET_ALLOW;
/* Make sure cross-thread synced filter points somewhere sane. */
struct seccomp_filter *f =
@@ -198,11 +263,6 @@ static u32 seccomp_run_filters(const struct seccomp_data *sd,
if (WARN_ON(f == NULL))
return SECCOMP_RET_KILL_PROCESS;
- if (!sd) {
- populate_seccomp_data(&sd_local);
- sd = &sd_local;
- }
-
/*
* All filters in the list are evaluated and the lowest BPF return
* value always takes priority (ignoring the DATA).
@@ -392,6 +452,7 @@ static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
if (!sfilter)
return ERR_PTR(-ENOMEM);
+ mutex_init(&sfilter->notify_lock);
ret = bpf_prog_create_from_user(&sfilter->prog, fprog,
seccomp_check_filter, save_orig);
if (ret < 0) {
@@ -485,7 +546,6 @@ static long seccomp_attach_filter(unsigned int flags,
static void __get_seccomp_filter(struct seccomp_filter *filter)
{
- /* Reference count is bounded by the number of total processes. */
refcount_inc(&filter->usage);
}
@@ -556,11 +616,13 @@ static void seccomp_send_sigsys(int syscall, int reason)
#define SECCOMP_LOG_TRACE (1 << 4)
#define SECCOMP_LOG_LOG (1 << 5)
#define SECCOMP_LOG_ALLOW (1 << 6)
+#define SECCOMP_LOG_USER_NOTIF (1 << 7)
static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS |
SECCOMP_LOG_KILL_THREAD |
SECCOMP_LOG_TRAP |
SECCOMP_LOG_ERRNO |
+ SECCOMP_LOG_USER_NOTIF |
SECCOMP_LOG_TRACE |
SECCOMP_LOG_LOG;
@@ -581,6 +643,9 @@ static inline void seccomp_log(unsigned long syscall, long signr, u32 action,
case SECCOMP_RET_TRACE:
log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE;
break;
+ case SECCOMP_RET_USER_NOTIF:
+ log = requested && seccomp_actions_logged & SECCOMP_LOG_USER_NOTIF;
+ break;
case SECCOMP_RET_LOG:
log = seccomp_actions_logged & SECCOMP_LOG_LOG;
break;
@@ -652,12 +717,75 @@ void secure_computing_strict(int this_syscall)
#else
#ifdef CONFIG_SECCOMP_FILTER
+static u64 seccomp_next_notify_id(struct seccomp_filter *filter)
+{
+ /*
+ * Note: overflow is ok here, the id just needs to be unique per
+ * filter.
+ */
+ lockdep_assert_held(&filter->notify_lock);
+ return filter->notif->next_id++;
+}
+
+static void seccomp_do_user_notification(int this_syscall,
+ struct seccomp_filter *match,
+ const struct seccomp_data *sd)
+{
+ int err;
+ long ret = 0;
+ struct seccomp_knotif n = {};
+
+ mutex_lock(&match->notify_lock);
+ err = -ENOSYS;
+ if (!match->notif)
+ goto out;
+
+ n.task = current;
+ n.state = SECCOMP_NOTIFY_INIT;
+ n.data = sd;
+ n.id = seccomp_next_notify_id(match);
+ init_completion(&n.ready);
+ list_add(&n.list, &match->notif->notifications);
+
+ up(&match->notif->request);
+ wake_up_poll(&match->notif->wqh, EPOLLIN | EPOLLRDNORM);
+ mutex_unlock(&match->notify_lock);
+
+ /*
+ * This is where we wait for a reply from userspace.
+ */
+ err = wait_for_completion_interruptible(&n.ready);
+ mutex_lock(&match->notify_lock);
+ if (err == 0) {
+ ret = n.val;
+ err = n.error;
+ }
+
+ /*
+ * Note that it's possible the listener died in between the time when
+ * we were notified of a respons (or a signal) and when we were able to
+ * re-acquire the lock, so only delete from the list if the
+ * notification actually exists.
+ *
+ * Also note that this test is only valid because there's no way to
+ * *reattach* to a notifier right now. If one is added, we'll need to
+ * keep track of the notif itself and make sure they match here.
+ */
+ if (match->notif)
+ list_del(&n.list);
+out:
+ mutex_unlock(&match->notify_lock);
+ syscall_set_return_value(current, task_pt_regs(current),
+ err, ret);
+}
+
static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
const bool recheck_after_trace)
{
u32 filter_ret, action;
struct seccomp_filter *match = NULL;
int data;
+ struct seccomp_data sd_local;
/*
* Make sure that any changes to mode from another thread have
@@ -665,6 +793,11 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
*/
rmb();
+ if (!sd) {
+ populate_seccomp_data(&sd_local);
+ sd = &sd_local;
+ }
+
filter_ret = seccomp_run_filters(sd, &match);
data = filter_ret & SECCOMP_RET_DATA;
action = filter_ret & SECCOMP_RET_ACTION_FULL;
@@ -728,6 +861,10 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
return 0;
+ case SECCOMP_RET_USER_NOTIF:
+ seccomp_do_user_notification(this_syscall, match, sd);
+ goto skip;
+
case SECCOMP_RET_LOG:
seccomp_log(this_syscall, 0, action, true);
return 0;
@@ -834,6 +971,262 @@ out:
}
#ifdef CONFIG_SECCOMP_FILTER
+static int seccomp_notify_release(struct inode *inode, struct file *file)
+{
+ struct seccomp_filter *filter = file->private_data;
+ struct seccomp_knotif *knotif;
+
+ mutex_lock(&filter->notify_lock);
+
+ /*
+ * If this file is being closed because e.g. the task who owned it
+ * died, let's wake everyone up who was waiting on us.
+ */
+ list_for_each_entry(knotif, &filter->notif->notifications, list) {
+ if (knotif->state == SECCOMP_NOTIFY_REPLIED)
+ continue;
+
+ knotif->state = SECCOMP_NOTIFY_REPLIED;
+ knotif->error = -ENOSYS;
+ knotif->val = 0;
+
+ complete(&knotif->ready);
+ }
+
+ kfree(filter->notif);
+ filter->notif = NULL;
+ mutex_unlock(&filter->notify_lock);
+ __put_seccomp_filter(filter);
+ return 0;
+}
+
+static long seccomp_notify_recv(struct seccomp_filter *filter,
+ void __user *buf)
+{
+ struct seccomp_knotif *knotif = NULL, *cur;
+ struct seccomp_notif unotif;
+ ssize_t ret;
+
+ memset(&unotif, 0, sizeof(unotif));
+
+ ret = down_interruptible(&filter->notif->request);
+ if (ret < 0)
+ return ret;
+
+ mutex_lock(&filter->notify_lock);
+ list_for_each_entry(cur, &filter->notif->notifications, list) {
+ if (cur->state == SECCOMP_NOTIFY_INIT) {
+ knotif = cur;
+ break;
+ }
+ }
+
+ /*
+ * If we didn't find a notification, it could be that the task was
+ * interrupted by a fatal signal between the time we were woken and
+ * when we were able to acquire the rw lock.
+ */
+ if (!knotif) {
+ ret = -ENOENT;
+ goto out;
+ }
+
+ unotif.id = knotif->id;
+ unotif.pid = task_pid_vnr(knotif->task);
+ unotif.data = *(knotif->data);
+
+ knotif->state = SECCOMP_NOTIFY_SENT;
+ wake_up_poll(&filter->notif->wqh, EPOLLOUT | EPOLLWRNORM);
+ ret = 0;
+out:
+ mutex_unlock(&filter->notify_lock);
+
+ if (ret == 0 && copy_to_user(buf, &unotif, sizeof(unotif))) {
+ ret = -EFAULT;
+
+ /*
+ * Userspace screwed up. To make sure that we keep this
+ * notification alive, let's reset it back to INIT. It
+ * may have died when we released the lock, so we need to make
+ * sure it's still around.
+ */
+ knotif = NULL;
+ mutex_lock(&filter->notify_lock);
+ list_for_each_entry(cur, &filter->notif->notifications, list) {
+ if (cur->id == unotif.id) {
+ knotif = cur;
+ break;
+ }
+ }
+
+ if (knotif) {
+ knotif->state = SECCOMP_NOTIFY_INIT;
+ up(&filter->notif->request);
+ }
+ mutex_unlock(&filter->notify_lock);
+ }
+
+ return ret;
+}
+
+static long seccomp_notify_send(struct seccomp_filter *filter,
+ void __user *buf)
+{
+ struct seccomp_notif_resp resp = {};
+ struct seccomp_knotif *knotif = NULL, *cur;
+ long ret;
+
+ if (copy_from_user(&resp, buf, sizeof(resp)))
+ return -EFAULT;
+
+ if (resp.flags)
+ return -EINVAL;
+
+ ret = mutex_lock_interruptible(&filter->notify_lock);
+ if (ret < 0)
+ return ret;
+
+ list_for_each_entry(cur, &filter->notif->notifications, list) {
+ if (cur->id == resp.id) {
+ knotif = cur;
+ break;
+ }
+ }
+
+ if (!knotif) {
+ ret = -ENOENT;
+ goto out;
+ }
+
+ /* Allow exactly one reply. */
+ if (knotif->state != SECCOMP_NOTIFY_SENT) {
+ ret = -EINPROGRESS;
+ goto out;
+ }
+
+ ret = 0;
+ knotif->state = SECCOMP_NOTIFY_REPLIED;
+ knotif->error = resp.error;
+ knotif->val = resp.val;
+ complete(&knotif->ready);
+out:
+ mutex_unlock(&filter->notify_lock);
+ return ret;
+}
+
+static long seccomp_notify_id_valid(struct seccomp_filter *filter,
+ void __user *buf)
+{
+ struct seccomp_knotif *knotif = NULL;
+ u64 id;
+ long ret;
+
+ if (copy_from_user(&id, buf, sizeof(id)))
+ return -EFAULT;
+
+ ret = mutex_lock_interruptible(&filter->notify_lock);
+ if (ret < 0)
+ return ret;
+
+ ret = -ENOENT;
+ list_for_each_entry(knotif, &filter->notif->notifications, list) {
+ if (knotif->id == id) {
+ if (knotif->state == SECCOMP_NOTIFY_SENT)
+ ret = 0;
+ goto out;
+ }
+ }
+
+out:
+ mutex_unlock(&filter->notify_lock);
+ return ret;
+}
+
+static long seccomp_notify_ioctl(struct file *file, unsigned int cmd,
+ unsigned long arg)
+{
+ struct seccomp_filter *filter = file->private_data;
+ void __user *buf = (void __user *)arg;
+
+ switch (cmd) {
+ case SECCOMP_IOCTL_NOTIF_RECV:
+ return seccomp_notify_recv(filter, buf);
+ case SECCOMP_IOCTL_NOTIF_SEND:
+ return seccomp_notify_send(filter, buf);
+ case SECCOMP_IOCTL_NOTIF_ID_VALID:
+ return seccomp_notify_id_valid(filter, buf);
+ default:
+ return -EINVAL;
+ }
+}
+
+static __poll_t seccomp_notify_poll(struct file *file,
+ struct poll_table_struct *poll_tab)
+{
+ struct seccomp_filter *filter = file->private_data;
+ __poll_t ret = 0;
+ struct seccomp_knotif *cur;
+
+ poll_wait(file, &filter->notif->wqh, poll_tab);
+
+ if (mutex_lock_interruptible(&filter->notify_lock) < 0)
+ return EPOLLERR;
+
+ list_for_each_entry(cur, &filter->notif->notifications, list) {
+ if (cur->state == SECCOMP_NOTIFY_INIT)
+ ret |= EPOLLIN | EPOLLRDNORM;
+ if (cur->state == SECCOMP_NOTIFY_SENT)
+ ret |= EPOLLOUT | EPOLLWRNORM;
+ if ((ret & EPOLLIN) && (ret & EPOLLOUT))
+ break;
+ }
+
+ mutex_unlock(&filter->notify_lock);
+
+ return ret;
+}
+
+static const struct file_operations seccomp_notify_ops = {
+ .poll = seccomp_notify_poll,
+ .release = seccomp_notify_release,
+ .unlocked_ioctl = seccomp_notify_ioctl,
+};
+
+static struct file *init_listener(struct seccomp_filter *filter)
+{
+ struct file *ret = ERR_PTR(-EBUSY);
+ struct seccomp_filter *cur;
+
+ for (cur = current->seccomp.filter; cur; cur = cur->prev) {
+ if (cur->notif)
+ goto out;
+ }
+
+ ret = ERR_PTR(-ENOMEM);
+ filter->notif = kzalloc(sizeof(*(filter->notif)), GFP_KERNEL);
+ if (!filter->notif)
+ goto out;
+
+ sema_init(&filter->notif->request, 0);
+ filter->notif->next_id = get_random_u64();
+ INIT_LIST_HEAD(&filter->notif->notifications);
+ init_waitqueue_head(&filter->notif->wqh);
+
+ ret = anon_inode_getfile("seccomp notify", &seccomp_notify_ops,
+ filter, O_RDWR);
+ if (IS_ERR(ret))
+ goto out_notif;
+
+ /* The file has a reference to it now */
+ __get_seccomp_filter(filter);
+
+out_notif:
+ if (IS_ERR(ret))
+ kfree(filter->notif);
+out:
+ return ret;
+}
+
/**
* seccomp_set_mode_filter: internal function for setting seccomp filter
* @flags: flags to change filter behavior
@@ -853,6 +1246,8 @@ static long seccomp_set_mode_filter(unsigned int flags,
const unsigned long seccomp_mode = SECCOMP_MODE_FILTER;
struct seccomp_filter *prepared = NULL;
long ret = -EINVAL;
+ int listener = -1;
+ struct file *listener_f = NULL;
/* Validate flags. */
if (flags & ~SECCOMP_FILTER_FLAG_MASK)
@@ -863,13 +1258,28 @@ static long seccomp_set_mode_filter(unsigned int flags,
if (IS_ERR(prepared))
return PTR_ERR(prepared);
+ if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
+ listener = get_unused_fd_flags(O_CLOEXEC);
+ if (listener < 0) {
+ ret = listener;
+ goto out_free;
+ }
+
+ listener_f = init_listener(prepared);
+ if (IS_ERR(listener_f)) {
+ put_unused_fd(listener);
+ ret = PTR_ERR(listener_f);
+ goto out_free;
+ }
+ }
+
/*
* Make sure we cannot change seccomp or nnp state via TSYNC
* while another thread is in the middle of calling exec.
*/
if (flags & SECCOMP_FILTER_FLAG_TSYNC &&
mutex_lock_killable(&current->signal->cred_guard_mutex))
- goto out_free;
+ goto out_put_fd;
spin_lock_irq(&current->sighand->siglock);
@@ -887,6 +1297,16 @@ out:
spin_unlock_irq(&current->sighand->siglock);
if (flags & SECCOMP_FILTER_FLAG_TSYNC)
mutex_unlock(&current->signal->cred_guard_mutex);
+out_put_fd:
+ if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
+ if (ret < 0) {
+ fput(listener_f);
+ put_unused_fd(listener);
+ } else {
+ fd_install(listener, listener_f);
+ ret = listener;
+ }
+ }
out_free:
seccomp_filter_free(prepared);
return ret;
@@ -911,6 +1331,7 @@ static long seccomp_get_action_avail(const char __user *uaction)
case SECCOMP_RET_KILL_THREAD:
case SECCOMP_RET_TRAP:
case SECCOMP_RET_ERRNO:
+ case SECCOMP_RET_USER_NOTIF:
case SECCOMP_RET_TRACE:
case SECCOMP_RET_LOG:
case SECCOMP_RET_ALLOW:
@@ -922,9 +1343,23 @@ static long seccomp_get_action_avail(const char __user *uaction)
return 0;
}
+static long seccomp_get_notif_sizes(void __user *usizes)
+{
+ struct seccomp_notif_sizes sizes = {
+ .seccomp_notif = sizeof(struct seccomp_notif),
+ .seccomp_notif_resp = sizeof(struct seccomp_notif_resp),
+ .seccomp_data = sizeof(struct seccomp_data),
+ };
+
+ if (copy_to_user(usizes, &sizes, sizeof(sizes)))
+ return -EFAULT;
+
+ return 0;
+}
+
/* Common entry point for both prctl and syscall. */
static long do_seccomp(unsigned int op, unsigned int flags,
- const char __user *uargs)
+ void __user *uargs)
{
switch (op) {
case SECCOMP_SET_MODE_STRICT:
@@ -938,13 +1373,18 @@ static long do_seccomp(unsigned int op, unsigned int flags,
return -EINVAL;
return seccomp_get_action_avail(uargs);
+ case SECCOMP_GET_NOTIF_SIZES:
+ if (flags != 0)
+ return -EINVAL;
+
+ return seccomp_get_notif_sizes(uargs);
default:
return -EINVAL;
}
}
SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags,
- const char __user *, uargs)
+ void __user *, uargs)
{
return do_seccomp(op, flags, uargs);
}
@@ -956,10 +1396,10 @@ SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags,
*
* Returns 0 on success or -EINVAL on failure.
*/
-long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter)
+long prctl_set_seccomp(unsigned long seccomp_mode, void __user *filter)
{
unsigned int op;
- char __user *uargs;
+ void __user *uargs;
switch (seccomp_mode) {
case SECCOMP_MODE_STRICT:
@@ -1111,6 +1551,7 @@ long seccomp_get_metadata(struct task_struct *task,
#define SECCOMP_RET_KILL_THREAD_NAME "kill_thread"
#define SECCOMP_RET_TRAP_NAME "trap"
#define SECCOMP_RET_ERRNO_NAME "errno"
+#define SECCOMP_RET_USER_NOTIF_NAME "user_notif"
#define SECCOMP_RET_TRACE_NAME "trace"
#define SECCOMP_RET_LOG_NAME "log"
#define SECCOMP_RET_ALLOW_NAME "allow"
@@ -1120,6 +1561,7 @@ static const char seccomp_actions_avail[] =
SECCOMP_RET_KILL_THREAD_NAME " "
SECCOMP_RET_TRAP_NAME " "
SECCOMP_RET_ERRNO_NAME " "
+ SECCOMP_RET_USER_NOTIF_NAME " "
SECCOMP_RET_TRACE_NAME " "
SECCOMP_RET_LOG_NAME " "
SECCOMP_RET_ALLOW_NAME;
@@ -1134,6 +1576,7 @@ static const struct seccomp_log_name seccomp_log_names[] = {
{ SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME },
{ SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME },
{ SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME },
+ { SECCOMP_LOG_USER_NOTIF, SECCOMP_RET_USER_NOTIF_NAME },
{ SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME },
{ SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME },
{ SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME },
diff --git a/samples/seccomp/.gitignore b/samples/seccomp/.gitignore
index 78fb78184291..d1e2e817d556 100644
--- a/samples/seccomp/.gitignore
+++ b/samples/seccomp/.gitignore
@@ -1,3 +1,4 @@
bpf-direct
bpf-fancy
dropper
+user-trap
diff --git a/samples/seccomp/Makefile b/samples/seccomp/Makefile
index cf34ff6b4065..4920903c8009 100644
--- a/samples/seccomp/Makefile
+++ b/samples/seccomp/Makefile
@@ -1,6 +1,6 @@
# SPDX-License-Identifier: GPL-2.0
ifndef CROSS_COMPILE
-hostprogs-$(CONFIG_SAMPLE_SECCOMP) := bpf-fancy dropper bpf-direct
+hostprogs-$(CONFIG_SAMPLE_SECCOMP) := bpf-fancy dropper bpf-direct user-trap
HOSTCFLAGS_bpf-fancy.o += -I$(objtree)/usr/include
HOSTCFLAGS_bpf-fancy.o += -idirafter $(objtree)/include
@@ -16,6 +16,10 @@ HOSTCFLAGS_bpf-direct.o += -I$(objtree)/usr/include
HOSTCFLAGS_bpf-direct.o += -idirafter $(objtree)/include
bpf-direct-objs := bpf-direct.o
+HOSTCFLAGS_user-trap.o += -I$(objtree)/usr/include
+HOSTCFLAGS_user-trap.o += -idirafter $(objtree)/include
+user-trap-objs := user-trap.o
+
# Try to match the kernel target.
ifndef CONFIG_64BIT
@@ -33,6 +37,7 @@ HOSTCFLAGS_bpf-fancy.o += $(MFLAG)
HOSTLDLIBS_bpf-direct += $(MFLAG)
HOSTLDLIBS_bpf-fancy += $(MFLAG)
HOSTLDLIBS_dropper += $(MFLAG)
+HOSTLDLIBS_user-trap += $(MFLAG)
endif
always := $(hostprogs-m)
endif
diff --git a/samples/seccomp/user-trap.c b/samples/seccomp/user-trap.c
new file mode 100644
index 000000000000..6d0125ca8af7
--- /dev/null
+++ b/samples/seccomp/user-trap.c
@@ -0,0 +1,375 @@
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <stddef.h>
+#include <sys/sysmacros.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <sys/syscall.h>
+#include <sys/user.h>
+#include <sys/ioctl.h>
+#include <sys/ptrace.h>
+#include <sys/mount.h>
+#include <linux/limits.h>
+#include <linux/filter.h>
+#include <linux/seccomp.h>
+
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof(*(x)))
+
+static int seccomp(unsigned int op, unsigned int flags, void *args)
+{
+ errno = 0;
+ return syscall(__NR_seccomp, op, flags, args);
+}
+
+static int send_fd(int sock, int fd)
+{
+ struct msghdr msg = {};
+ struct cmsghdr *cmsg;
+ char buf[CMSG_SPACE(sizeof(int))] = {0}, c = 'c';
+ struct iovec io = {
+ .iov_base = &c,
+ .iov_len = 1,
+ };
+
+ msg.msg_iov = &io;
+ msg.msg_iovlen = 1;
+ msg.msg_control = buf;
+ msg.msg_controllen = sizeof(buf);
+ cmsg = CMSG_FIRSTHDR(&msg);
+ cmsg->cmsg_level = SOL_SOCKET;
+ cmsg->cmsg_type = SCM_RIGHTS;
+ cmsg->cmsg_len = CMSG_LEN(sizeof(int));
+ *((int *)CMSG_DATA(cmsg)) = fd;
+ msg.msg_controllen = cmsg->cmsg_len;
+
+ if (sendmsg(sock, &msg, 0) < 0) {
+ perror("sendmsg");
+ return -1;
+ }
+
+ return 0;
+}
+
+static int recv_fd(int sock)
+{
+ struct msghdr msg = {};
+ struct cmsghdr *cmsg;
+ char buf[CMSG_SPACE(sizeof(int))] = {0}, c = 'c';
+ struct iovec io = {
+ .iov_base = &c,
+ .iov_len = 1,
+ };
+
+ msg.msg_iov = &io;
+ msg.msg_iovlen = 1;
+ msg.msg_control = buf;
+ msg.msg_controllen = sizeof(buf);
+
+ if (recvmsg(sock, &msg, 0) < 0) {
+ perror("recvmsg");
+ return -1;
+ }
+
+ cmsg = CMSG_FIRSTHDR(&msg);
+
+ return *((int *)CMSG_DATA(cmsg));
+}
+
+static int user_trap_syscall(int nr, unsigned int flags)
+{
+ struct sock_filter filter[] = {
+ BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
+ offsetof(struct seccomp_data, nr)),
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, nr, 0, 1),
+ BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_USER_NOTIF),
+ BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+ };
+
+ struct sock_fprog prog = {
+ .len = (unsigned short)ARRAY_SIZE(filter),
+ .filter = filter,
+ };
+
+ return seccomp(SECCOMP_SET_MODE_FILTER, flags, &prog);
+}
+
+static int handle_req(struct seccomp_notif *req,
+ struct seccomp_notif_resp *resp, int listener)
+{
+ char path[PATH_MAX], source[PATH_MAX], target[PATH_MAX];
+ int ret = -1, mem;
+
+ resp->id = req->id;
+ resp->error = -EPERM;
+ resp->val = 0;
+
+ if (req->data.nr != __NR_mount) {
+ fprintf(stderr, "huh? trapped something besides mount? %d\n", req->data.nr);
+ return -1;
+ }
+
+ /* Only allow bind mounts. */
+ if (!(req->data.args[3] & MS_BIND))
+ return 0;
+
+ /*
+ * Ok, let's read the task's memory to see where they wanted their
+ * mount to go.
+ */
+ snprintf(path, sizeof(path), "/proc/%d/mem", req->pid);
+ mem = open(path, O_RDONLY);
+ if (mem < 0) {
+ perror("open mem");
+ return -1;
+ }
+
+ /*
+ * Now we avoid a TOCTOU: we referred to a pid by its pid, but since
+ * the pid that made the syscall may have died, we need to confirm that
+ * the pid is still valid after we open its /proc/pid/mem file. We can
+ * ask the listener fd this as follows.
+ *
+ * Note that this check should occur *after* any task-specific
+ * resources are opened, to make sure that the task has not died and
+ * we're not wrongly reading someone else's state in order to make
+ * decisions.
+ */
+ if (ioctl(listener, SECCOMP_IOCTL_NOTIF_ID_VALID, &req->id) < 0) {
+ fprintf(stderr, "task died before we could map its memory\n");
+ goto out;
+ }
+
+ /*
+ * Phew, we've got the right /proc/pid/mem. Now we can read it. Note
+ * that to avoid another TOCTOU, we should read all of the pointer args
+ * before we decide to allow the syscall.
+ */
+ if (lseek(mem, req->data.args[0], SEEK_SET) < 0) {
+ perror("seek");
+ goto out;
+ }
+
+ ret = read(mem, source, sizeof(source));
+ if (ret < 0) {
+ perror("read");
+ goto out;
+ }
+
+ if (lseek(mem, req->data.args[1], SEEK_SET) < 0) {
+ perror("seek");
+ goto out;
+ }
+
+ ret = read(mem, target, sizeof(target));
+ if (ret < 0) {
+ perror("read");
+ goto out;
+ }
+
+ /*
+ * Our policy is to only allow bind mounts inside /tmp. This isn't very
+ * interesting, because we could do unprivlieged bind mounts with user
+ * namespaces already, but you get the idea.
+ */
+ if (!strncmp(source, "/tmp/", 5) && !strncmp(target, "/tmp/", 5)) {
+ if (mount(source, target, NULL, req->data.args[3], NULL) < 0) {
+ ret = -1;
+ perror("actual mount");
+ goto out;
+ }
+ resp->error = 0;
+ }
+
+ /* Even if we didn't allow it because of policy, generating the
+ * response was be a success, because we want to tell the worker EPERM.
+ */
+ ret = 0;
+
+out:
+ close(mem);
+ return ret;
+}
+
+int main(void)
+{
+ int sk_pair[2], ret = 1, status, listener;
+ pid_t worker = 0 , tracer = 0;
+
+ if (socketpair(PF_LOCAL, SOCK_SEQPACKET, 0, sk_pair) < 0) {
+ perror("socketpair");
+ return 1;
+ }
+
+ worker = fork();
+ if (worker < 0) {
+ perror("fork");
+ goto close_pair;
+ }
+
+ if (worker == 0) {
+ listener = user_trap_syscall(__NR_mount,
+ SECCOMP_FILTER_FLAG_NEW_LISTENER);
+ if (listener < 0) {
+ perror("seccomp");
+ exit(1);
+ }
+
+ /*
+ * Drop privileges. We definitely can't mount as uid 1000.
+ */
+ if (setuid(1000) < 0) {
+ perror("setuid");
+ exit(1);
+ }
+
+ /*
+ * Send the listener to the parent; also serves as
+ * synchronization.
+ */
+ if (send_fd(sk_pair[1], listener) < 0)
+ exit(1);
+ close(listener);
+
+ if (mkdir("/tmp/foo", 0755) < 0) {
+ perror("mkdir");
+ exit(1);
+ }
+
+ /*
+ * Try a bad mount just for grins.
+ */
+ if (mount("/dev/sda", "/tmp/foo", NULL, 0, NULL) != -1) {
+ fprintf(stderr, "huh? mounted /dev/sda?\n");
+ exit(1);
+ }
+
+ if (errno != EPERM) {
+ perror("bad error from mount");
+ exit(1);
+ }
+
+ /*
+ * Ok, we expect this one to succeed.
+ */
+ if (mount("/tmp/foo", "/tmp/foo", NULL, MS_BIND, NULL) < 0) {
+ perror("mount");
+ exit(1);
+ }
+
+ exit(0);
+ }
+
+ /*
+ * Get the listener from the child.
+ */
+ listener = recv_fd(sk_pair[0]);
+ if (listener < 0)
+ goto out_kill;
+
+ /*
+ * Fork a task to handle the requests. This isn't strictly necessary,
+ * but it makes the particular writing of this sample easier, since we
+ * can just wait ofr the tracee to exit and kill the tracer.
+ */
+ tracer = fork();
+ if (tracer < 0) {
+ perror("fork");
+ goto out_kill;
+ }
+
+ if (tracer == 0) {
+ struct seccomp_notif *req;
+ struct seccomp_notif_resp *resp;
+ struct seccomp_notif_sizes sizes;
+
+ if (seccomp(SECCOMP_GET_NOTIF_SIZES, 0, &sizes) < 0) {
+ perror("seccomp(GET_NOTIF_SIZES)");
+ goto out_close;
+ }
+
+ req = malloc(sizes.seccomp_notif);
+ if (!req)
+ goto out_close;
+ memset(req, 0, sizeof(*req));
+
+ resp = malloc(sizes.seccomp_notif_resp);
+ if (!resp)
+ goto out_req;
+ memset(resp, 0, sizeof(*resp));
+
+ while (1) {
+ if (ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, req)) {
+ perror("ioctl recv");
+ goto out_resp;
+ }
+
+ if (handle_req(req, resp, listener) < 0)
+ goto out_resp;
+
+ /*
+ * ENOENT here means that the task may have gotten a
+ * signal and restarted the syscall. It's up to the
+ * handler to decide what to do in this case, but for
+ * the sample code, we just ignore it. Probably
+ * something better should happen, like undoing the
+ * mount, or keeping track of the args to make sure we
+ * don't do it again.
+ */
+ if (ioctl(listener, SECCOMP_IOCTL_NOTIF_SEND, resp) < 0 &&
+ errno != ENOENT) {
+ perror("ioctl send");
+ goto out_resp;
+ }
+ }
+out_resp:
+ free(resp);
+out_req:
+ free(req);
+out_close:
+ close(listener);
+ exit(1);
+ }
+
+ close(listener);
+
+ if (waitpid(worker, &status, 0) != worker) {
+ perror("waitpid");
+ goto out_kill;
+ }
+
+ if (umount2("/tmp/foo", MNT_DETACH) < 0 && errno != EINVAL) {
+ perror("umount2");
+ goto out_kill;
+ }
+
+ if (remove("/tmp/foo") < 0 && errno != ENOENT) {
+ perror("remove");
+ exit(1);
+ }
+
+ if (!WIFEXITED(status) || WEXITSTATUS(status)) {
+ fprintf(stderr, "worker exited nonzero\n");
+ goto out_kill;
+ }
+
+ ret = 0;
+
+out_kill:
+ if (tracer > 0)
+ kill(tracer, SIGKILL);
+ if (worker > 0)
+ kill(worker, SIGKILL);
+
+close_pair:
+ close(sk_pair[0]);
+ close(sk_pair[1]);
+ return ret;
+}
diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
index c9a2abf8be1b..067cb4607d6c 100644
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -5,6 +5,7 @@
* Test code for seccomp bpf.
*/
+#define _GNU_SOURCE
#include <sys/types.h>
/*
@@ -40,10 +41,12 @@
#include <sys/fcntl.h>
#include <sys/mman.h>
#include <sys/times.h>
+#include <sys/socket.h>
+#include <sys/ioctl.h>
-#define _GNU_SOURCE
#include <unistd.h>
#include <sys/syscall.h>
+#include <poll.h>
#include "../kselftest_harness.h"
@@ -133,6 +136,10 @@ struct seccomp_data {
#define SECCOMP_GET_ACTION_AVAIL 2
#endif
+#ifndef SECCOMP_GET_NOTIF_SIZES
+#define SECCOMP_GET_NOTIF_SIZES 3
+#endif
+
#ifndef SECCOMP_FILTER_FLAG_TSYNC
#define SECCOMP_FILTER_FLAG_TSYNC (1UL << 0)
#endif
@@ -154,6 +161,44 @@ struct seccomp_metadata {
};
#endif
+#ifndef SECCOMP_FILTER_FLAG_NEW_LISTENER
+#define SECCOMP_FILTER_FLAG_NEW_LISTENER (1UL << 3)
+
+#define SECCOMP_RET_USER_NOTIF 0x7fc00000U
+
+#define SECCOMP_IOC_MAGIC '!'
+#define SECCOMP_IO(nr) _IO(SECCOMP_IOC_MAGIC, nr)
+#define SECCOMP_IOR(nr, type) _IOR(SECCOMP_IOC_MAGIC, nr, type)
+#define SECCOMP_IOW(nr, type) _IOW(SECCOMP_IOC_MAGIC, nr, type)
+#define SECCOMP_IOWR(nr, type) _IOWR(SECCOMP_IOC_MAGIC, nr, type)
+
+/* Flags for seccomp notification fd ioctl. */
+#define SECCOMP_IOCTL_NOTIF_RECV SECCOMP_IOWR(0, struct seccomp_notif)
+#define SECCOMP_IOCTL_NOTIF_SEND SECCOMP_IOWR(1, \
+ struct seccomp_notif_resp)
+#define SECCOMP_IOCTL_NOTIF_ID_VALID SECCOMP_IOR(2, __u64)
+
+struct seccomp_notif {
+ __u64 id;
+ __u32 pid;
+ __u32 flags;
+ struct seccomp_data data;
+};
+
+struct seccomp_notif_resp {
+ __u64 id;
+ __s64 val;
+ __s32 error;
+ __u32 flags;
+};
+
+struct seccomp_notif_sizes {
+ __u16 seccomp_notif;
+ __u16 seccomp_notif_resp;
+ __u16 seccomp_data;
+};
+#endif
+
#ifndef seccomp
int seccomp(unsigned int op, unsigned int flags, void *args)
{
@@ -2077,7 +2122,8 @@ TEST(detect_seccomp_filter_flags)
{
unsigned int flags[] = { SECCOMP_FILTER_FLAG_TSYNC,
SECCOMP_FILTER_FLAG_LOG,
- SECCOMP_FILTER_FLAG_SPEC_ALLOW };
+ SECCOMP_FILTER_FLAG_SPEC_ALLOW,
+ SECCOMP_FILTER_FLAG_NEW_LISTENER };
unsigned int flag, all_flags;
int i;
long ret;
@@ -2938,6 +2984,403 @@ skip:
ASSERT_EQ(0, kill(pid, SIGKILL));
}
+static int user_trap_syscall(int nr, unsigned int flags)
+{
+ struct sock_filter filter[] = {
+ BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
+ offsetof(struct seccomp_data, nr)),
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, nr, 0, 1),
+ BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_USER_NOTIF),
+ BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+ };
+
+ struct sock_fprog prog = {
+ .len = (unsigned short)ARRAY_SIZE(filter),
+ .filter = filter,
+ };
+
+ return seccomp(SECCOMP_SET_MODE_FILTER, flags, &prog);
+}
+
+#define USER_NOTIF_MAGIC 116983961184613L
+TEST(user_notification_basic)
+{
+ pid_t pid;
+ long ret;
+ int status, listener;
+ struct seccomp_notif req = {};
+ struct seccomp_notif_resp resp = {};
+ struct pollfd pollfd;
+
+ struct sock_filter filter[] = {
+ BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+ };
+ struct sock_fprog prog = {
+ .len = (unsigned short)ARRAY_SIZE(filter),
+ .filter = filter,
+ };
+
+ pid = fork();
+ ASSERT_GE(pid, 0);
+
+ /* Check that we get -ENOSYS with no listener attached */
+ if (pid == 0) {
+ if (user_trap_syscall(__NR_getpid, 0) < 0)
+ exit(1);
+ ret = syscall(__NR_getpid);
+ exit(ret >= 0 || errno != ENOSYS);
+ }
+
+ EXPECT_EQ(waitpid(pid, &status, 0), pid);
+ EXPECT_EQ(true, WIFEXITED(status));
+ EXPECT_EQ(0, WEXITSTATUS(status));
+
+ /* Add some no-op filters so for grins. */
+ EXPECT_EQ(seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog), 0);
+ EXPECT_EQ(seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog), 0);
+ EXPECT_EQ(seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog), 0);
+ EXPECT_EQ(seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog), 0);
+
+ /* Check that the basic notification machinery works */
+ listener = user_trap_syscall(__NR_getpid,
+ SECCOMP_FILTER_FLAG_NEW_LISTENER);
+ EXPECT_GE(listener, 0);
+
+ /* Installing a second listener in the chain should EBUSY */
+ EXPECT_EQ(user_trap_syscall(__NR_getpid,
+ SECCOMP_FILTER_FLAG_NEW_LISTENER),
+ -1);
+ EXPECT_EQ(errno, EBUSY);
+
+ pid = fork();
+ ASSERT_GE(pid, 0);
+
+ if (pid == 0) {
+ ret = syscall(__NR_getpid);
+ exit(ret != USER_NOTIF_MAGIC);
+ }
+
+ pollfd.fd = listener;
+ pollfd.events = POLLIN | POLLOUT;
+
+ EXPECT_GT(poll(&pollfd, 1, -1), 0);
+ EXPECT_EQ(pollfd.revents, POLLIN);
+
+ EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0);
+
+ pollfd.fd = listener;
+ pollfd.events = POLLIN | POLLOUT;
+
+ EXPECT_GT(poll(&pollfd, 1, -1), 0);
+ EXPECT_EQ(pollfd.revents, POLLOUT);
+
+ EXPECT_EQ(req.data.nr, __NR_getpid);
+
+ resp.id = req.id;
+ resp.error = 0;
+ resp.val = USER_NOTIF_MAGIC;
+
+ /* check that we make sure flags == 0 */
+ resp.flags = 1;
+ EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_SEND, &resp), -1);
+ EXPECT_EQ(errno, EINVAL);
+
+ resp.flags = 0;
+ EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_SEND, &resp), 0);
+
+ EXPECT_EQ(waitpid(pid, &status, 0), pid);
+ EXPECT_EQ(true, WIFEXITED(status));
+ EXPECT_EQ(0, WEXITSTATUS(status));
+}
+
+TEST(user_notification_kill_in_middle)
+{
+ pid_t pid;
+ long ret;
+ int listener;
+ struct seccomp_notif req = {};
+ struct seccomp_notif_resp resp = {};
+
+ listener = user_trap_syscall(__NR_getpid,
+ SECCOMP_FILTER_FLAG_NEW_LISTENER);
+ EXPECT_GE(listener, 0);
+
+ /*
+ * Check that nothing bad happens when we kill the task in the middle
+ * of a syscall.
+ */
+ pid = fork();
+ ASSERT_GE(pid, 0);
+
+ if (pid == 0) {
+ ret = syscall(__NR_getpid);
+ exit(ret != USER_NOTIF_MAGIC);
+ }
+
+ EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0);
+ EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_ID_VALID, &req.id), 0);
+
+ EXPECT_EQ(kill(pid, SIGKILL), 0);
+ EXPECT_EQ(waitpid(pid, NULL, 0), pid);
+
+ EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_ID_VALID, &req.id), -1);
+
+ resp.id = req.id;
+ ret = ioctl(listener, SECCOMP_IOCTL_NOTIF_SEND, &resp);
+ EXPECT_EQ(ret, -1);
+ EXPECT_EQ(errno, ENOENT);
+}
+
+static int handled = -1;
+
+static void signal_handler(int signal)
+{
+ if (write(handled, "c", 1) != 1)
+ perror("write from signal");
+}
+
+TEST(user_notification_signal)
+{
+ pid_t pid;
+ long ret;
+ int status, listener, sk_pair[2];
+ struct seccomp_notif req = {};
+ struct seccomp_notif_resp resp = {};
+ char c;
+
+ ASSERT_EQ(socketpair(PF_LOCAL, SOCK_SEQPACKET, 0, sk_pair), 0);
+
+ listener = user_trap_syscall(__NR_gettid,
+ SECCOMP_FILTER_FLAG_NEW_LISTENER);
+ EXPECT_GE(listener, 0);
+
+ pid = fork();
+ ASSERT_GE(pid, 0);
+
+ if (pid == 0) {
+ close(sk_pair[0]);
+ handled = sk_pair[1];
+ if (signal(SIGUSR1, signal_handler) == SIG_ERR) {
+ perror("signal");
+ exit(1);
+ }
+ /*
+ * ERESTARTSYS behavior is a bit hard to test, because we need
+ * to rely on a signal that has not yet been handled. Let's at
+ * least check that the error code gets propagated through, and
+ * hope that it doesn't break when there is actually a signal :)
+ */
+ ret = syscall(__NR_gettid);
+ exit(!(ret == -1 && errno == 512));
+ }
+
+ close(sk_pair[1]);
+
+ EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0);
+
+ EXPECT_EQ(kill(pid, SIGUSR1), 0);
+
+ /*
+ * Make sure the signal really is delivered, which means we're not
+ * stuck in the user notification code any more and the notification
+ * should be dead.
+ */
+ EXPECT_EQ(read(sk_pair[0], &c, 1), 1);
+
+ resp.id = req.id;
+ resp.error = -EPERM;
+ resp.val = 0;
+
+ EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_SEND, &resp), -1);
+ EXPECT_EQ(errno, ENOENT);
+
+ EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0);
+
+ resp.id = req.id;
+ resp.error = -512; /* -ERESTARTSYS */
+ resp.val = 0;
+
+ EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_SEND, &resp), 0);
+
+ EXPECT_EQ(waitpid(pid, &status, 0), pid);
+ EXPECT_EQ(true, WIFEXITED(status));
+ EXPECT_EQ(0, WEXITSTATUS(status));
+}
+
+TEST(user_notification_closed_listener)
+{
+ pid_t pid;
+ long ret;
+ int status, listener;
+
+ listener = user_trap_syscall(__NR_getpid,
+ SECCOMP_FILTER_FLAG_NEW_LISTENER);
+ EXPECT_GE(listener, 0);
+
+ /*
+ * Check that we get an ENOSYS when the listener is closed.
+ */
+ pid = fork();
+ ASSERT_GE(pid, 0);
+ if (pid == 0) {
+ close(listener);
+ ret = syscall(__NR_getpid);
+ exit(ret != -1 && errno != ENOSYS);
+ }
+
+ close(listener);
+
+ EXPECT_EQ(waitpid(pid, &status, 0), pid);
+ EXPECT_EQ(true, WIFEXITED(status));
+ EXPECT_EQ(0, WEXITSTATUS(status));
+}
+
+/*
+ * Check that a pid in a child namespace still shows up as valid in ours.
+ */
+TEST(user_notification_child_pid_ns)
+{
+ pid_t pid;
+ int status, listener;
+ struct seccomp_notif req = {};
+ struct seccomp_notif_resp resp = {};
+
+ ASSERT_EQ(unshare(CLONE_NEWPID), 0);
+
+ listener = user_trap_syscall(__NR_getpid, SECCOMP_FILTER_FLAG_NEW_LISTENER);
+ ASSERT_GE(listener, 0);
+
+ pid = fork();
+ ASSERT_GE(pid, 0);
+
+ if (pid == 0)
+ exit(syscall(__NR_getpid) != USER_NOTIF_MAGIC);
+
+ EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0);
+ EXPECT_EQ(req.pid, pid);
+
+ resp.id = req.id;
+ resp.error = 0;
+ resp.val = USER_NOTIF_MAGIC;
+
+ EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_SEND, &resp), 0);
+
+ EXPECT_EQ(waitpid(pid, &status, 0), pid);
+ EXPECT_EQ(true, WIFEXITED(status));
+ EXPECT_EQ(0, WEXITSTATUS(status));
+ close(listener);
+}
+
+/*
+ * Check that a pid in a sibling (i.e. unrelated) namespace shows up as 0, i.e.
+ * invalid.
+ */
+TEST(user_notification_sibling_pid_ns)
+{
+ pid_t pid, pid2;
+ int status, listener;
+ struct seccomp_notif req = {};
+ struct seccomp_notif_resp resp = {};
+
+ listener = user_trap_syscall(__NR_getpid, SECCOMP_FILTER_FLAG_NEW_LISTENER);
+ ASSERT_GE(listener, 0);
+
+ pid = fork();
+ ASSERT_GE(pid, 0);
+
+ if (pid == 0) {
+ ASSERT_EQ(unshare(CLONE_NEWPID), 0);
+
+ pid2 = fork();
+ ASSERT_GE(pid2, 0);
+
+ if (pid2 == 0)
+ exit(syscall(__NR_getpid) != USER_NOTIF_MAGIC);
+
+ EXPECT_EQ(waitpid(pid2, &status, 0), pid2);
+ EXPECT_EQ(true, WIFEXITED(status));
+ EXPECT_EQ(0, WEXITSTATUS(status));
+ exit(WEXITSTATUS(status));
+ }
+
+ /* Create the sibling ns, and sibling in it. */
+ EXPECT_EQ(unshare(CLONE_NEWPID), 0);
+ EXPECT_EQ(errno, 0);
+
+ pid2 = fork();
+ EXPECT_GE(pid2, 0);
+
+ if (pid2 == 0) {
+ ASSERT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0);
+ /*
+ * The pid should be 0, i.e. the task is in some namespace that
+ * we can't "see".
+ */
+ ASSERT_EQ(req.pid, 0);
+
+ resp.id = req.id;
+ resp.error = 0;
+ resp.val = USER_NOTIF_MAGIC;
+
+ ASSERT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_SEND, &resp), 0);
+ exit(0);
+ }
+
+ close(listener);
+
+ EXPECT_EQ(waitpid(pid, &status, 0), pid);
+ EXPECT_EQ(true, WIFEXITED(status));
+ EXPECT_EQ(0, WEXITSTATUS(status));
+
+ EXPECT_EQ(waitpid(pid2, &status, 0), pid2);
+ EXPECT_EQ(true, WIFEXITED(status));
+ EXPECT_EQ(0, WEXITSTATUS(status));
+}
+
+TEST(user_notification_fault_recv)
+{
+ pid_t pid;
+ int status, listener;
+ struct seccomp_notif req = {};
+ struct seccomp_notif_resp resp = {};
+
+ listener = user_trap_syscall(__NR_getpid, SECCOMP_FILTER_FLAG_NEW_LISTENER);
+ ASSERT_GE(listener, 0);
+
+ pid = fork();
+ ASSERT_GE(pid, 0);
+
+ if (pid == 0)
+ exit(syscall(__NR_getpid) != USER_NOTIF_MAGIC);
+
+ /* Do a bad recv() */
+ EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, NULL), -1);
+ EXPECT_EQ(errno, EFAULT);
+
+ /* We should still be able to receive this notification, though. */
+ EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0);
+ EXPECT_EQ(req.pid, pid);
+
+ resp.id = req.id;
+ resp.error = 0;
+ resp.val = USER_NOTIF_MAGIC;
+
+ EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_SEND, &resp), 0);
+
+ EXPECT_EQ(waitpid(pid, &status, 0), pid);
+ EXPECT_EQ(true, WIFEXITED(status));
+ EXPECT_EQ(0, WEXITSTATUS(status));
+}
+
+TEST(seccomp_get_notif_sizes)
+{
+ struct seccomp_notif_sizes sizes;
+
+ EXPECT_EQ(seccomp(SECCOMP_GET_NOTIF_SIZES, 0, &sizes), 0);
+ EXPECT_EQ(sizes.seccomp_notif, sizeof(struct seccomp_notif));
+ EXPECT_EQ(sizes.seccomp_notif_resp, sizeof(struct seccomp_notif_resp));
+}
+
/*
* TODO:
* - add microbenchmarks