From: "Darrick J. Wong" djwong@kernel.org
[ Upstream commit 97cf79677ecb50a38517253ae2fd705849a7e51a ]
KASAN reported a UAF bug when I was running xfs/235:
BUG: KASAN: use-after-free in xlog_recover_process_intents+0xa77/0xae0 [xfs] Read of size 8 at addr ffff88804391b360 by task mount/5680
CPU: 2 PID: 5680 Comm: mount Not tainted 6.0.0-xfsx #6.0.0 77e7b52a4943a975441e5ac90a5ad7748b7867f6 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x34/0x44 print_report.cold+0x2cc/0x682 kasan_report+0xa3/0x120 xlog_recover_process_intents+0xa77/0xae0 [xfs fb841c7180aad3f8359438576e27867f5795667e] xlog_recover_finish+0x7d/0x970 [xfs fb841c7180aad3f8359438576e27867f5795667e] xfs_log_mount_finish+0x2d7/0x5d0 [xfs fb841c7180aad3f8359438576e27867f5795667e] xfs_mountfs+0x11d4/0x1d10 [xfs fb841c7180aad3f8359438576e27867f5795667e] xfs_fs_fill_super+0x13d5/0x1a80 [xfs fb841c7180aad3f8359438576e27867f5795667e] get_tree_bdev+0x3da/0x6e0 vfs_get_tree+0x7d/0x240 path_mount+0xdd3/0x17d0 __x64_sys_mount+0x1fa/0x270 do_syscall_64+0x2b/0x80 entry_SYSCALL_64_after_hwframe+0x46/0xb0 RIP: 0033:0x7ff5bc069eae Code: 48 8b 0d 85 1f 0f 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 52 1f 0f 00 f7 d8 64 89 01 48 RSP: 002b:00007ffe433fd448 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007ff5bc069eae RDX: 00005575d7213290 RSI: 00005575d72132d0 RDI: 00005575d72132b0 RBP: 00005575d7212fd0 R08: 00005575d7213230 R09: 00005575d7213fe0 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00005575d7213290 R14: 00005575d72132b0 R15: 00005575d7212fd0 </TASK>
Allocated by task 5680: kasan_save_stack+0x1e/0x40 __kasan_slab_alloc+0x66/0x80 kmem_cache_alloc+0x152/0x320 xfs_rui_init+0x17a/0x1b0 [xfs] xlog_recover_rui_commit_pass2+0xb9/0x2e0 [xfs] xlog_recover_items_pass2+0xe9/0x220 [xfs] xlog_recover_commit_trans+0x673/0x900 [xfs] xlog_recovery_process_trans+0xbe/0x130 [xfs] xlog_recover_process_data+0x103/0x2a0 [xfs] xlog_do_recovery_pass+0x548/0xc60 [xfs] xlog_do_log_recovery+0x62/0xc0 [xfs] xlog_do_recover+0x73/0x480 [xfs] xlog_recover+0x229/0x460 [xfs] xfs_log_mount+0x284/0x640 [xfs] xfs_mountfs+0xf8b/0x1d10 [xfs] xfs_fs_fill_super+0x13d5/0x1a80 [xfs] get_tree_bdev+0x3da/0x6e0 vfs_get_tree+0x7d/0x240 path_mount+0xdd3/0x17d0 __x64_sys_mount+0x1fa/0x270 do_syscall_64+0x2b/0x80 entry_SYSCALL_64_after_hwframe+0x46/0xb0
Freed by task 5680: kasan_save_stack+0x1e/0x40 kasan_set_track+0x21/0x30 kasan_set_free_info+0x20/0x30 ____kasan_slab_free+0x144/0x1b0 slab_free_freelist_hook+0xab/0x180 kmem_cache_free+0x1f1/0x410 xfs_rud_item_release+0x33/0x80 [xfs] xfs_trans_free_items+0xc3/0x220 [xfs] xfs_trans_cancel+0x1fa/0x590 [xfs] xfs_rui_item_recover+0x913/0xd60 [xfs] xlog_recover_process_intents+0x24e/0xae0 [xfs] xlog_recover_finish+0x7d/0x970 [xfs] xfs_log_mount_finish+0x2d7/0x5d0 [xfs] xfs_mountfs+0x11d4/0x1d10 [xfs] xfs_fs_fill_super+0x13d5/0x1a80 [xfs] get_tree_bdev+0x3da/0x6e0 vfs_get_tree+0x7d/0x240 path_mount+0xdd3/0x17d0 __x64_sys_mount+0x1fa/0x270 do_syscall_64+0x2b/0x80 entry_SYSCALL_64_after_hwframe+0x46/0xb0
The buggy address belongs to the object at ffff88804391b300 which belongs to the cache xfs_rui_item of size 688 The buggy address is located 96 bytes inside of 688-byte region [ffff88804391b300, ffff88804391b5b0)
The buggy address belongs to the physical page: page:ffffea00010e4600 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888043919320 pfn:0x43918 head:ffffea00010e4600 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4fff80000010200(slab|head|node=1|zone=1|lastcpupid=0xfff) raw: 04fff80000010200 0000000000000000 dead000000000122 ffff88807f0eadc0 raw: ffff888043919320 0000000080140010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected
Memory state around the buggy address: ffff88804391b200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88804391b280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88804391b300: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^ ffff88804391b380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88804391b400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================
The test fuzzes an rmap btree block and starts writer threads to induce a filesystem shutdown on the corrupt block. When the filesystem is remounted, recovery will try to replay the committed rmap intent item, but the corruption problem causes the recovery transaction to fail. Cancelling the transaction frees the RUD, which frees the RUI that we recovered.
When we return to xlog_recover_process_intents, @lip is now a dangling pointer, and we cannot use it to find the iop_recover method for the tracepoint. Hence we must store the item ops before calling ->iop_recover if we want to give it to the tracepoint so that the trace data will tell us exactly which intent item failed.
Signed-off-by: Darrick J. Wong djwong@kernel.org Reviewed-by: Christoph Hellwig hch@lst.de Signed-off-by: Leah Rumancik leah.rumancik@gmail.com Acked-by: Chandan Babu R chandanbabu@kernel.org --- fs/xfs/xfs_log_recover.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c index 04961ebf16ea..3d844a250b71 100644 --- a/fs/xfs/xfs_log_recover.c +++ b/fs/xfs/xfs_log_recover.c @@ -2560,6 +2560,7 @@ xlog_recover_process_intents( for (lip = xfs_trans_ail_cursor_first(ailp, &cur, 0); lip != NULL; lip = xfs_trans_ail_cursor_next(ailp, &cur)) { + const struct xfs_item_ops *ops; /* * We're done when we see something other than an intent. * There should be no intents left in the AIL now. @@ -2584,13 +2585,17 @@ xlog_recover_process_intents( * deferred ops, you /must/ attach them to the capture list in * the recover routine or else those subsequent intents will be * replayed in the wrong order! + * + * The recovery function can free the log item, so we must not + * access lip after it returns. */ spin_unlock(&ailp->ail_lock); - error = lip->li_ops->iop_recover(lip, &capture_list); + ops = lip->li_ops; + error = ops->iop_recover(lip, &capture_list); spin_lock(&ailp->ail_lock); if (error) { trace_xlog_intent_recovery_failed(log->l_mp, error, - lip->li_ops->iop_recover); + ops->iop_recover); break; } }