diff options
| author | Jan Kara <jack@suse.cz> | 2019-04-24 19:39:57 +0300 |
|---|---|---|
| committer | Jan Kara <jack@suse.cz> | 2019-04-28 23:14:50 +0300 |
| commit | b1da6a51871c6929dced1a7fad81990988b36ed6 (patch) | |
| tree | 2c487de5f9e6369a9ee459e93d10dd37f094e945 /fs/notify/mark.c | |
| parent | ba25b50d582ff6c6021eee80824134aeb9ab8785 (diff) | |
| download | linux-b1da6a51871c6929dced1a7fad81990988b36ed6.tar.xz | |
fsnotify: Fix NULL ptr deref in fanotify_get_fsid()
fanotify_get_fsid() is reading mark->connector->fsid under srcu. It can
happen that it sees mark not fully initialized or mark that is already
detached from the object list. In these cases mark->connector
can be NULL leading to NULL ptr dereference. Fix the problem by
being careful when reading mark->connector and check it for being NULL.
Also use WRITE_ONCE when writing the mark just to prevent compiler from
doing something stupid.
Reported-by: syzbot+15927486a4f1bfcbaf91@syzkaller.appspotmail.com
Fixes: 77115225acc6 ("fanotify: cache fsid in fsnotify_mark_connector")
Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs/notify/mark.c')
| -rw-r--r-- | fs/notify/mark.c | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/fs/notify/mark.c b/fs/notify/mark.c index d593d4269561..22acb0a79b53 100644 --- a/fs/notify/mark.c +++ b/fs/notify/mark.c @@ -239,13 +239,13 @@ static void fsnotify_drop_object(unsigned int type, void *objp) void fsnotify_put_mark(struct fsnotify_mark *mark) { - struct fsnotify_mark_connector *conn; + struct fsnotify_mark_connector *conn = READ_ONCE(mark->connector); void *objp = NULL; unsigned int type = FSNOTIFY_OBJ_TYPE_DETACHED; bool free_conn = false; /* Catch marks that were actually never attached to object */ - if (!mark->connector) { + if (!conn) { if (refcount_dec_and_test(&mark->refcnt)) fsnotify_final_mark_destroy(mark); return; @@ -255,10 +255,9 @@ void fsnotify_put_mark(struct fsnotify_mark *mark) * We have to be careful so that traversals of obj_list under lock can * safely grab mark reference. */ - if (!refcount_dec_and_lock(&mark->refcnt, &mark->connector->lock)) + if (!refcount_dec_and_lock(&mark->refcnt, &conn->lock)) return; - conn = mark->connector; hlist_del_init_rcu(&mark->obj_list); if (hlist_empty(&conn->list)) { objp = fsnotify_detach_connector_from_object(conn, &type); @@ -266,7 +265,7 @@ void fsnotify_put_mark(struct fsnotify_mark *mark) } else { __fsnotify_recalc_mask(conn); } - mark->connector = NULL; + WRITE_ONCE(mark->connector, NULL); spin_unlock(&conn->lock); fsnotify_drop_object(type, objp); @@ -620,7 +619,7 @@ restart: /* mark should be the last entry. last is the current last entry */ hlist_add_behind_rcu(&mark->obj_list, &last->obj_list); added: - mark->connector = conn; + WRITE_ONCE(mark->connector, conn); out_err: spin_unlock(&conn->lock); spin_unlock(&mark->lock); @@ -808,6 +807,7 @@ void fsnotify_init_mark(struct fsnotify_mark *mark, refcount_set(&mark->refcnt, 1); fsnotify_get_group(group); mark->group = group; + WRITE_ONCE(mark->connector, NULL); } /* |