From 409e873ea3c1fd3079909718bbeb06ac1ec7f38b Mon Sep 17 00:00:00 2001 From: Xiubo Li Date: Thu, 1 Jun 2023 08:59:31 +0800 Subject: ceph: fix use-after-free bug for inodes when flushing capsnaps There is a race between capsnaps flush and removing the inode from 'mdsc->snap_flush_list' list: == Thread A == == Thread B == ceph_queue_cap_snap() -> allocate 'capsnapA' ->ihold('&ci->vfs_inode') ->add 'capsnapA' to 'ci->i_cap_snaps' ->add 'ci' to 'mdsc->snap_flush_list' ... == Thread C == ceph_flush_snaps() ->__ceph_flush_snaps() ->__send_flush_snap() handle_cap_flushsnap_ack() ->iput('&ci->vfs_inode') this also will release 'ci' ... == Thread D == ceph_handle_snap() ->flush_snaps() ->iterate 'mdsc->snap_flush_list' ->get the stale 'ci' ->remove 'ci' from ->ihold(&ci->vfs_inode) this 'mdsc->snap_flush_list' will WARNING To fix this we will increase the inode's i_count ref when adding 'ci' to the 'mdsc->snap_flush_list' list. [ idryomov: need_put int -> bool ] Cc: stable@vger.kernel.org Link: https://bugzilla.redhat.com/show_bug.cgi?id=2209299 Signed-off-by: Xiubo Li Reviewed-by: Milind Changire Reviewed-by: Ilya Dryomov Signed-off-by: Ilya Dryomov --- fs/ceph/snap.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'fs/ceph/snap.c') diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c index 0b236ebd989f..2e73ba62bd7a 100644 --- a/fs/ceph/snap.c +++ b/fs/ceph/snap.c @@ -693,8 +693,10 @@ int __ceph_finish_cap_snap(struct ceph_inode_info *ci, capsnap->size); spin_lock(&mdsc->snap_flush_lock); - if (list_empty(&ci->i_snap_flush_item)) + if (list_empty(&ci->i_snap_flush_item)) { + ihold(inode); list_add_tail(&ci->i_snap_flush_item, &mdsc->snap_flush_list); + } spin_unlock(&mdsc->snap_flush_lock); return 1; /* caller may want to ceph_flush_snaps */ } -- cgit v1.2.3