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-rw-r--r--kernel/seccomp.c17
1 files changed, 15 insertions, 2 deletions
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 54a0347ca812..4b51d9cbcf06 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -502,7 +502,10 @@ out:
*
* Caller must be holding current->sighand->siglock lock.
*
- * Returns 0 on success, -ve on error.
+ * Returns 0 on success, -ve on error, or
+ * - in TSYNC mode: the pid of a thread which was either not in the correct
+ * seccomp mode or did not have an ancestral seccomp filter
+ * - in NEW_LISTENER mode: the fd of the new listener
*/
static long seccomp_attach_filter(unsigned int flags,
struct seccomp_filter *filter)
@@ -1258,6 +1261,16 @@ static long seccomp_set_mode_filter(unsigned int flags,
if (flags & ~SECCOMP_FILTER_FLAG_MASK)
return -EINVAL;
+ /*
+ * In the successful case, NEW_LISTENER returns the new listener fd.
+ * But in the failure case, TSYNC returns the thread that died. If you
+ * combine these two flags, there's no way to tell whether something
+ * succeeded or failed. So, let's disallow this combination.
+ */
+ if ((flags & SECCOMP_FILTER_FLAG_TSYNC) &&
+ (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER))
+ return -EINVAL;
+
/* Prepare the new filter before holding any locks. */
prepared = seccomp_prepare_user_filter(filter);
if (IS_ERR(prepared))
@@ -1304,7 +1317,7 @@ out:
mutex_unlock(&current->signal->cred_guard_mutex);
out_put_fd:
if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
- if (ret < 0) {
+ if (ret) {
listener_f->private_data = NULL;
fput(listener_f);
put_unused_fd(listener);