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authorTycho Andersen <tycho@docker.com>2017-10-11 09:39:20 -0600
committerKees Cook <keescook@chromium.org>2017-11-28 15:36:01 -0800
commitf06eae831f0c1fc5b982ea200daf552810e1dd55 (patch)
tree47b087ab2288fb3f975947e28992c7c35c3e19c2 /kernel/seccomp.c
parent4fbd8d194f06c8a3fd2af1ce560ddb31f7ec8323 (diff)
downloadlinux-stericsson-f06eae831f0c1fc5b982ea200daf552810e1dd55.tar.gz
seccomp: hoist out filter resolving logic
Hoist out the nth filter resolving logic that ptrace uses into a new function. We'll use this in the next patch to implement the new PTRACE_SECCOMP_GET_FILTER_FLAGS command. Signed-off-by: Tycho Andersen <tycho@docker.com> CC: Kees Cook <keescook@chromium.org> CC: Andy Lutomirski <luto@amacapital.net> CC: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'kernel/seccomp.c')
-rw-r--r--kernel/seccomp.c77
1 files changed, 45 insertions, 32 deletions
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 5f0dfb2abb8d..99bddaf79076 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -978,49 +978,68 @@ long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter)
}
#if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
-long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
- void __user *data)
+static struct seccomp_filter *get_nth_filter(struct task_struct *task,
+ unsigned long filter_off)
{
- struct seccomp_filter *filter;
- struct sock_fprog_kern *fprog;
- long ret;
- unsigned long count = 0;
-
- if (!capable(CAP_SYS_ADMIN) ||
- current->seccomp.mode != SECCOMP_MODE_DISABLED) {
- return -EACCES;
- }
+ struct seccomp_filter *orig, *filter;
+ unsigned long count;
+ /*
+ * Note: this is only correct because the caller should be the (ptrace)
+ * tracer of the task, otherwise lock_task_sighand is needed.
+ */
spin_lock_irq(&task->sighand->siglock);
+
if (task->seccomp.mode != SECCOMP_MODE_FILTER) {
- ret = -EINVAL;
- goto out;
+ spin_unlock_irq(&task->sighand->siglock);
+ return ERR_PTR(-EINVAL);
}
- filter = task->seccomp.filter;
- while (filter) {
- filter = filter->prev;
+ orig = task->seccomp.filter;
+ __get_seccomp_filter(orig);
+ spin_unlock_irq(&task->sighand->siglock);
+
+ count = 0;
+ for (filter = orig; filter; filter = filter->prev)
count++;
- }
if (filter_off >= count) {
- ret = -ENOENT;
+ filter = ERR_PTR(-ENOENT);
goto out;
}
- count -= filter_off;
- filter = task->seccomp.filter;
- while (filter && count > 1) {
- filter = filter->prev;
+ count -= filter_off;
+ for (filter = orig; filter && count > 1; filter = filter->prev)
count--;
- }
if (WARN_ON(count != 1 || !filter)) {
- /* The filter tree shouldn't shrink while we're using it. */
- ret = -ENOENT;
+ filter = ERR_PTR(-ENOENT);
goto out;
}
+ __get_seccomp_filter(filter);
+
+out:
+ __put_seccomp_filter(orig);
+ return filter;
+}
+
+long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
+ void __user *data)
+{
+ struct seccomp_filter *filter;
+ struct sock_fprog_kern *fprog;
+ long ret;
+
+ if (!capable(CAP_SYS_ADMIN) ||
+ current->seccomp.mode != SECCOMP_MODE_DISABLED) {
+ return -EACCES;
+ }
+
+ filter = get_nth_filter(task, filter_off);
+ if (IS_ERR(filter))
+ return PTR_ERR(filter);
+
fprog = filter->prog->orig_prog;
if (!fprog) {
/* This must be a new non-cBPF filter, since we save
@@ -1035,17 +1054,11 @@ long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
if (!data)
goto out;
- __get_seccomp_filter(filter);
- spin_unlock_irq(&task->sighand->siglock);
-
if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog)))
ret = -EFAULT;
- __put_seccomp_filter(filter);
- return ret;
-
out:
- spin_unlock_irq(&task->sighand->siglock);
+ __put_seccomp_filter(filter);
return ret;
}
#endif