Hi Chandan, Please pull this branch with changes for xfs for 6.8-rc1. As usual, I did a test-merge with the main upstream branch as of a few minutes ago, and didn't see any conflicts. Please let me know if you encounter any problems. --D The following changes since commit 33cc938e65a98f1d29d0a18403dbbee050dcad9a: Linux 6.7-rc4 (2023-12-03 18:52:56 +0900) are available in the Git repository at: https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git tags/reconstruct-defer-work-6.8_2023-12-06 for you to fetch changes up to 67d70e02027c6a7419d0d8f1587ac84c4e3d580d: xfs: move ->iop_recover to xfs_defer_op_type (2023-12-06 18:17:23 -0800) ---------------------------------------------------------------- xfs: log intent item recovery should reconstruct defer work state [v3] Long Li reported a KASAN report from a UAF when intent recovery fails: ================================================================== BUG: KASAN: slab-use-after-free in xfs_cui_release+0xb7/0xc0 Read of size 4 at addr ffff888012575e60 by task kworker/u8:3/103 CPU: 3 PID: 103 Comm: kworker/u8:3 Not tainted 6.4.0-rc7-next-20230619-00003-g94543a53f9a4-dirty #166 Workqueue: xfs-cil/sda xlog_cil_push_work Call Trace: <TASK> dump_stack_lvl+0x50/0x70 print_report+0xc2/0x600 kasan_report+0xb6/0xe0 xfs_cui_release+0xb7/0xc0 xfs_cud_item_release+0x3c/0x90 xfs_trans_committed_bulk+0x2d5/0x7f0 xlog_cil_committed+0xaba/0xf20 xlog_cil_push_work+0x1a60/0x2360 process_one_work+0x78e/0x1140 worker_thread+0x58b/0xf60 kthread+0x2cd/0x3c0 ret_from_fork+0x1f/0x30 </TASK> Allocated by task 531: kasan_save_stack+0x22/0x40 kasan_set_track+0x25/0x30 __kasan_slab_alloc+0x55/0x60 kmem_cache_alloc+0x195/0x5f0 xfs_cui_init+0x198/0x1d0 xlog_recover_cui_commit_pass2+0x133/0x5f0 xlog_recover_items_pass2+0x107/0x230 xlog_recover_commit_trans+0x3e7/0x9c0 xlog_recovery_process_trans+0x140/0x1d0 xlog_recover_process_ophdr+0x1a0/0x3d0 xlog_recover_process_data+0x108/0x2d0 xlog_recover_process+0x1f6/0x280 xlog_do_recovery_pass+0x609/0xdb0 xlog_do_log_recovery+0x84/0xe0 xlog_do_recover+0x7d/0x470 xlog_recover+0x25f/0x490 xfs_log_mount+0x2dd/0x6f0 xfs_mountfs+0x11ce/0x1e70 xfs_fs_fill_super+0x10ec/0x1b20 get_tree_bdev+0x3c8/0x730 vfs_get_tree+0x89/0x2c0 path_mount+0xecf/0x1800 do_mount+0xf3/0x110 __x64_sys_mount+0x154/0x1f0 do_syscall_64+0x39/0x80 entry_SYSCALL_64_after_hwframe+0x63/0xcd Freed by task 531: kasan_save_stack+0x22/0x40 kasan_set_track+0x25/0x30 kasan_save_free_info+0x2b/0x40 __kasan_slab_free+0x114/0x1b0 kmem_cache_free+0xf8/0x510 xfs_cui_item_free+0x95/0xb0 xfs_cui_release+0x86/0xc0 xlog_recover_cancel_intents.isra.0+0xf8/0x210 xlog_recover_finish+0x7e7/0x980 xfs_log_mount_finish+0x2bb/0x4a0 xfs_mountfs+0x14bf/0x1e70 xfs_fs_fill_super+0x10ec/0x1b20 get_tree_bdev+0x3c8/0x730 vfs_get_tree+0x89/0x2c0 path_mount+0xecf/0x1800 do_mount+0xf3/0x110 __x64_sys_mount+0x154/0x1f0 do_syscall_64+0x39/0x80 entry_SYSCALL_64_after_hwframe+0x63/0xcd The buggy address belongs to the object at ffff888012575dc8 which belongs to the cache xfs_cui_item of size 432 The buggy address is located 152 bytes inside of freed 432-byte region [ffff888012575dc8, ffff888012575f78) The buggy address belongs to the physical page: page:ffffea0000495d00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888012576208 pfn:0x12574 head:ffffea0000495d00 order:2 entire_mapcount:0 nr_pages_mapped:0 pincount:0 flags: 0x1fffff80010200(slab|head|node=0|zone=1|lastcpupid=0x1fffff) page_type: 0xffffffff() raw: 001fffff80010200 ffff888012092f40 ffff888014570150 ffff888014570150 raw: ffff888012576208 00000000001e0010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888012575d00: fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc fc ffff888012575d80: fc fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb >ffff888012575e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888012575e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888012575f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc ================================================================== "If process intents fails, intent items left in AIL will be delete from AIL and freed in error handling, even intent items that have been recovered and created done items. After this, uaf will be triggered when done item committed, because at this point the released intent item will be accessed. xlog_recover_finish xlog_cil_push_work ---------------------------- --------------------------- xlog_recover_process_intents xfs_cui_item_recover//cui_refcount == 1 xfs_trans_get_cud xfs_trans_commit <add cud item to cil> xfs_cui_item_recover <error occurred and return> xlog_recover_cancel_intents xfs_cui_release //cui_refcount == 0 xfs_cui_item_free //free cui <release other intent items> xlog_force_shutdown //shutdown <...> <push items in cil> xlog_cil_committed xfs_cud_item_release xfs_cui_release // UAF "Intent log items are created with a reference count of 2, one for the creator, and one for the intent done object. Log recovery explicitly drops the creator reference after it is inserted into the AIL, but it then processes the log item as if it also owns the intent-done reference. "The code in ->iop_recovery should assume that it passes the reference to the done intent, we can remove the intent item from the AIL after creating the done-intent, but if that code fails before creating the done-intent then it needs to release the intent reference by log recovery itself. "That way when we go to cancel the intent, the only intents we find in the AIL are the ones we know have not been processed yet and hence we can safely drop both the creator and the intent done reference from xlog_recover_cancel_intents(). "Hence if we remove the intent from the list of intents that need to be recovered after we have done the initial recovery, we acheive two things: "1. the tail of the log can be moved forward with the commit of the done intent or new intent to continue the operation, and "2. We avoid the problem of trying to determine how many reference counts we need to drop from intent recovery cancelling because we never come across intents we've actually attempted recovery on." Restated: The cause of the UAF is that xlog_recover_cancel_intents thinks that it owns the refcount on any intent item in the AIL, and that it's always safe to release these intent items. This is not true after the recovery function creates an log intent done item and points it at the log intent item because releasing the done item always releases the intent item. The runtime defer ops code avoids all this by tracking both the log intent and the intent done items, and releasing only the intent done item if both have been created. Long Li proposed fixing this by adding state flags, but I have a more comprehensive fix. First, observe that the latter half of the intent _recover functions are nearly open-coded versions of the corresponding _finish_one function that uses an onstack deferred work item to single-step through the item. Second, notice that the recover function is not an exact match because of the odd behavior that unfinished recovered work items are relogged with separate log intent items instead of a single new log intent item, which is what the defer ops machinery does. Dave and I have long suspected that recovery should be reconstructing the defer work state from what's in the recovered intent item. Now we finally have an excuse to refactor the code to do that. This series starts by fixing a resource leak in LARP recovery. We fix the bug that Long Li reported by switching the intent recovery code to construct chains of xfs_defer_pending objects and then using the defer pending objects to track the intent/done item ownership. Finally, we clean up the code to reconstruct the exact incore state, which means we can remove all the opencoded _recover code, which makes maintaining log items much easier. v2: minor changes per review comments v3: pick up more rvb tags, fix build errors This has been lightly tested with fstests. Enjoy! Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx> ---------------------------------------------------------------- Darrick J. Wong (8): xfs: don't leak recovered attri intent items xfs: use xfs_defer_pending objects to recover intent items xfs: pass the xfs_defer_pending object to iop_recover xfs: transfer recovered intent item ownership in ->iop_recover xfs: recreate work items when recovering intent items xfs: dump the recovered xattri log item if corruption happens xfs: use xfs_defer_finish_one to finish recovered work items xfs: move ->iop_recover to xfs_defer_op_type fs/xfs/libxfs/xfs_defer.c | 127 +++++++++++++++++++++++-------- fs/xfs/libxfs/xfs_defer.h | 19 +++++ fs/xfs/libxfs/xfs_log_recover.h | 7 ++ fs/xfs/xfs_attr_item.c | 132 ++++++++++++++++---------------- fs/xfs/xfs_bmap_item.c | 102 +++++++++++++------------ fs/xfs/xfs_extfree_item.c | 127 ++++++++++++++----------------- fs/xfs/xfs_log.c | 1 + fs/xfs/xfs_log_priv.h | 1 + fs/xfs/xfs_log_recover.c | 129 +++++++++++++++++--------------- fs/xfs/xfs_refcount_item.c | 138 +++++++++++----------------------- fs/xfs/xfs_rmap_item.c | 161 ++++++++++++++++++++-------------------- fs/xfs/xfs_trans.h | 2 - 12 files changed, 492 insertions(+), 454 deletions(-)
