author: Linus Torvalds <torvalds@linux-foundation.org> 2019-07-10 20:09:17 -0700
committer: Linus Torvalds <torvalds@linux-foundation.org> 2019-07-10 20:09:17 -0700
commit: e6983afd9254c559acf67dd5f62df824d19851eb
parent: 988052f47adc5c3b0b004180b59bb3761d91b752
Commit Summary:
Diffstat:
1 file changed, 22 insertions, 0 deletions
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index a90bb19dcfa2..91006f47e420 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -920,6 +920,22 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
return 0;
}
+static int fanotify_events_supported(struct path *path, __u64 mask)
+{
+ /*
+ * Some filesystems such as 'proc' acquire unusual locks when opening
+ * files. For them fanotify permission events have high chances of
+ * deadlocking the system - open done when reporting fanotify event
+ * blocks on this "unusual" lock while another process holding the lock
+ * waits for fanotify permission event to be answered. Just disallow
+ * permission events for such filesystems.
+ */
+ if (mask & FANOTIFY_PERM_EVENTS &&
+ path->mnt->mnt_sb->s_type->fs_flags & FS_DISALLOW_NOTIFY_PERM)
+ return -EINVAL;
+ return 0;
+}
+
static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
int dfd, const char __user *pathname)
{
@@ -1018,6 +1034,12 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
if (ret)
goto fput_and_out;
+ if (flags & FAN_MARK_ADD) {
+ ret = fanotify_events_supported(&path, mask);
+ if (ret)
+ goto path_put_and_out;
+ }
+
if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
ret = fanotify_test_fid(&path, &__fsid);
if (ret)