path: root/kernel/seccomp.c
diff options
authorTyler Hicks <tyhicks@canonical.com>2018-05-04 01:08:14 +0000
committerPaul Moore <paul@paul-moore.com>2018-05-08 02:03:28 -0400
commitea6eca778500b0aaf6e5f10dac4d2cd745c2a50b (patch)
treee958134f8b0c3453331a51214b80b51302b40559 /kernel/seccomp.c
parentbeb44acaf000c97d6c89de581f377df5757857f3 (diff)
seccomp: Audit attempts to modify the actions_logged sysctl
The decision to log a seccomp action will always be subject to the value of the kernel.seccomp.actions_logged sysctl, even for processes that are being inspected via the audit subsystem, in an upcoming patch. Therefore, we need to emit an audit record on attempts at writing to the actions_logged sysctl when auditing is enabled. This patch updates the write handler for the actions_logged sysctl to emit an audit record on attempts to write to the sysctl. Successful writes to the sysctl will result in a record that includes a normalized list of logged actions in the "actions" field and a "res" field equal to 1. Unsuccessful writes to the sysctl will result in a record that doesn't include the "actions" field and has a "res" field equal to 0. Not all unsuccessful writes to the sysctl are audited. For example, an audit record will not be emitted if an unprivileged process attempts to open the sysctl file for reading since that access control check is not part of the sysctl's write handler. Below are some example audit records when writing various strings to the actions_logged sysctl. Writing "not-a-real-action", when the kernel.seccomp.actions_logged sysctl previously was "kill_process kill_thread trap errno trace log", emits this audit record: type=CONFIG_CHANGE msg=audit(1525392371.454:120): op=seccomp-logging actions=? old-actions=kill_process,kill_thread,trap,errno,trace,log res=0 If you then write "kill_process kill_thread errno trace log", this audit record is emitted: type=CONFIG_CHANGE msg=audit(1525392401.645:126): op=seccomp-logging actions=kill_process,kill_thread,errno,trace,log old-actions=kill_process,kill_thread,trap,errno,trace,log res=1 If you then write "log log errno trace kill_process kill_thread", which is unordered and contains the log action twice, it results in the same actions value as the previous record: type=CONFIG_CHANGE msg=audit(1525392436.354:132): op=seccomp-logging actions=kill_process,kill_thread,errno,trace,log old-actions=kill_process,kill_thread,errno,trace,log res=1 If you then write an empty string to the sysctl, this audit record is emitted: type=CONFIG_CHANGE msg=audit(1525392494.413:138): op=seccomp-logging actions=(none) old-actions=kill_process,kill_thread,errno,trace,log res=1 No audit records are generated when reading the actions_logged sysctl. Suggested-by: Steve Grubb <sgrubb@redhat.com> Signed-off-by: Tyler Hicks <tyhicks@canonical.com> Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: Paul Moore <paul@paul-moore.com>
Diffstat (limited to 'kernel/seccomp.c')
1 files changed, 49 insertions, 9 deletions
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index b36ac1e0cd0e..f5630d1a88fe 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -1219,11 +1219,10 @@ static int read_actions_logged(struct ctl_table *ro_table, void __user *buffer,
static int write_actions_logged(struct ctl_table *ro_table, void __user *buffer,
- size_t *lenp, loff_t *ppos)
+ size_t *lenp, loff_t *ppos, u32 *actions_logged)
char names[sizeof(seccomp_actions_avail)];
struct ctl_table table;
- u32 actions_logged;
int ret;
if (!capable(CAP_SYS_ADMIN))
@@ -1238,24 +1237,65 @@ static int write_actions_logged(struct ctl_table *ro_table, void __user *buffer,
if (ret)
return ret;
- if (!seccomp_actions_logged_from_names(&actions_logged, table.data))
+ if (!seccomp_actions_logged_from_names(actions_logged, table.data))
return -EINVAL;
- if (actions_logged & SECCOMP_LOG_ALLOW)
+ if (*actions_logged & SECCOMP_LOG_ALLOW)
return -EINVAL;
- seccomp_actions_logged = actions_logged;
+ seccomp_actions_logged = *actions_logged;
return 0;
+static void audit_actions_logged(u32 actions_logged, u32 old_actions_logged,
+ int ret)
+ char names[sizeof(seccomp_actions_avail)];
+ char old_names[sizeof(seccomp_actions_avail)];
+ const char *new = names;
+ const char *old = old_names;
+ if (!audit_enabled)
+ return;
+ memset(names, 0, sizeof(names));
+ memset(old_names, 0, sizeof(old_names));
+ if (ret)
+ new = "?";
+ else if (!actions_logged)
+ new = "(none)";
+ else if (!seccomp_names_from_actions_logged(names, sizeof(names),
+ actions_logged, ","))
+ new = "?";
+ if (!old_actions_logged)
+ old = "(none)";
+ else if (!seccomp_names_from_actions_logged(old_names,
+ sizeof(old_names),
+ old_actions_logged, ","))
+ old = "?";
+ return audit_seccomp_actions_logged(new, old, !ret);
static int seccomp_actions_logged_handler(struct ctl_table *ro_table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos)
- if (write)
- return write_actions_logged(ro_table, buffer, lenp, ppos);
- else
- return read_actions_logged(ro_table, buffer, lenp, ppos);
+ int ret;
+ if (write) {
+ u32 actions_logged = 0;
+ u32 old_actions_logged = seccomp_actions_logged;
+ ret = write_actions_logged(ro_table, buffer, lenp, ppos,
+ &actions_logged);
+ audit_actions_logged(actions_logged, old_actions_logged, ret);
+ } else
+ ret = read_actions_logged(ro_table, buffer, lenp, ppos);
+ return ret;
static struct ctl_path seccomp_sysctl_path[] = {