kernel/linux.git/fs/ceph/snap.c, branch v5.15.209

ceph: fix use-after-free bug for inodes when flushing capsnaps

2023-06-14T09:13:06+00:00

commit 409e873ea3c1fd3079909718bbeb06ac1ec7f38b upstream. 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 Signed-off-by: Greg Kroah-Hartman

ceph: force updating the msg pointer in non-split case

2023-05-24T16:36:55+00:00

commit 4cafd0400bcb6187c0d4ab4d4b0229a89ac4f8c2 upstream. When the MClientSnap reqeust's op is not CEPH_SNAP_OP_SPLIT the request may still contain a list of 'split_realms', and we need to skip it anyway. Or it will be parsed as a corrupt snaptrace. Cc: stable@vger.kernel.org Link: https://tracker.ceph.com/issues/61200 Reported-by: Frank Schilder Signed-off-by: Xiubo Li Reviewed-by: Ilya Dryomov Signed-off-by: Ilya Dryomov Signed-off-by: Greg Kroah-Hartman

ceph: avoid putting the realm twice when decoding snaps fails

2022-12-02T16:41:00+00:00

[ Upstream commit 51884d153f7ec85e18d607b2467820a90e0f4359 ] When decoding the snaps fails it maybe leaving the 'first_realm' and 'realm' pointing to the same snaprealm memory. And then it'll put it twice and could cause random use-after-free, BUG_ON, etc issues. Cc: stable@vger.kernel.org Link: https://tracker.ceph.com/issues/57686 Signed-off-by: Xiubo Li Reviewed-by: Ilya Dryomov Signed-off-by: Ilya Dryomov Signed-off-by: Sasha Levin

ceph: do not update snapshot context when there is no new snapshot

2022-12-02T16:41:00+00:00

[ Upstream commit 2e586641c950e7f3e7e008404bd783a466b9b590 ] We will only track the uppest parent snapshot realm from which we need to rebuild the snapshot contexts _downward_ in hierarchy. For all the others having no new snapshot we will do nothing. This fix will avoid calling ceph_queue_cap_snap() on some inodes inappropriately. For example, with the code in mainline, suppose there are 2 directory hierarchies (with 6 directories total), like this: /dir_X1/dir_X2/dir_X3/ /dir_Y1/dir_Y2/dir_Y3/ Firstly, make a snapshot under /dir_X1/dir_X2/.snap/snap_X2, then make a root snapshot under /.snap/root_snap. Every time we make snapshots under /dir_Y1/..., the kclient will always try to rebuild the snap context for snap_X2 realm and finally will always try to queue cap snaps for dir_Y2 and dir_Y3, which makes no sense. That's because the snap_X2's seq is 2 and root_snap's seq is 3. So when creating a new snapshot under /dir_Y1/... the new seq will be 4, and the mds will send the kclient a snapshot backtrace in _downward_ order: seqs 4, 3. When ceph_update_snap_trace() is called, it will always rebuild the from the last realm, that's the root_snap. So later when rebuilding the snap context, the current logic will always cause it to rebuild the snap_X2 realm and then try to queue cap snaps for all the inodes related in that realm, even though it's not necessary. This is accompanied by a lot of these sorts of dout messages: "ceph: queue_cap_snap 00000000a42b796b nothing dirty|writing" Fix the logic to avoid this situation. Also, the 'invalidate' word is not precise here. In actuality, it will cause a rebuild of the existing snapshot contexts or just build non-existent ones. Rename it to 'rebuild_snapcs'. URL: https://tracker.ceph.com/issues/44100 Signed-off-by: Xiubo Li Reviewed-by: Jeff Layton Signed-off-by: Ilya Dryomov Stable-dep-of: 51884d153f7e ("ceph: avoid putting the realm twice when decoding snaps fails") Signed-off-by: Sasha Levin

ceph: add ceph_change_snap_realm() helper

2021-09-02T20:49:17+00:00

Consolidate some fiddly code for changing an inode's snap_realm into a new helper function, and change the callers to use it. While we're in here, nothing uses the i_snap_realm_counter field, so remove that from the inode. Signed-off-by: Jeff Layton Reviewed-by: Luis Henriques Signed-off-by: Ilya Dryomov

ceph: correctly handle releasing an embedded cap flush

2021-08-25T14:34:11+00:00

The ceph_cap_flush structures are usually dynamically allocated, but the ceph_cap_snap has an embedded one. When force umounting, the client will try to remove all the session caps. During this, it will free them, but that should not be done with the ones embedded in a capsnap. Fix this by adding a new boolean that indicates that the cap flush is embedded in a capsnap, and skip freeing it if that's set. At the same time, switch to using list_del_init() when detaching the i_list and g_list heads. It's possible for a forced umount to remove these objects but then handle_cap_flushsnap_ack() races in and does the list_del_init() again, corrupting memory. Cc: stable@vger.kernel.org URL: https://tracker.ceph.com/issues/52283 Signed-off-by: Xiubo Li Reviewed-by: Jeff Layton Signed-off-by: Ilya Dryomov

ceph: take snap_empty_lock atomically with snaprealm refcount change

2021-08-04T17:20:29+00:00

There is a race in ceph_put_snap_realm. The change to the nref and the spinlock acquisition are not done atomically, so you could decrement nref, and before you take the spinlock, the nref is incremented again. At that point, you end up putting it on the empty list when it shouldn't be there. Eventually __cleanup_empty_realms runs and frees it when it's still in-use. Fix this by protecting the 1->0 transition with atomic_dec_and_lock, and just drop the spinlock if we can get the rwsem. Because these objects can also undergo a 0->1 refcount transition, we must protect that change as well with the spinlock. Increment locklessly unless the value is at 0, in which case we take the spinlock, increment and then take it off the empty list if it did the 0->1 transition. With these changes, I'm removing the dout() messages from these functions, as well as in __put_snap_realm. They've always been racy, and it's better to not print values that may be misleading. Cc: stable@vger.kernel.org URL: https://tracker.ceph.com/issues/46419 Reported-by: Mark Nelson Signed-off-by: Jeff Layton Reviewed-by: Luis Henriques Signed-off-by: Ilya Dryomov

ceph: eliminate ceph_async_iput()

2021-06-28T22:15:52+00:00

Now that we don't need to hold session->s_mutex or the snap_rwsem when calling ceph_check_caps, we can eliminate ceph_async_iput and just use normal iput calls. Signed-off-by: Jeff Layton Signed-off-by: Ilya Dryomov

ceph: don't take s_mutex in ceph_flush_snaps

2021-06-28T22:15:52+00:00

Signed-off-by: Jeff Layton Reviewed-by: Luis Henriques Signed-off-by: Ilya Dryomov

ceph: clean up locking annotation for ceph_get_snap_realm and __lookup_snap_realm

2021-06-28T22:15:51+00:00

They both say that the snap_rwsem must be held for write, but I don't see any real reason for it, and it's not currently always called that way. The lookup is just walking the rbtree, so holding it for read should be fine there. The "get" is bumping the refcount and (possibly) removing it from the empty list. I see no need to hold the snap_rwsem for write for that. Signed-off-by: Jeff Layton Reviewed-by: Ilya Dryomov Signed-off-by: Ilya Dryomov