From: Darrick J. Wong <djwong@xxxxxxxxxx>
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@xxxxxxxxxx>
---
fs/xfs/xfs_log_recover.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 17e923b9c5fa..322eb2ee6c55 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -2552,6 +2552,8 @@ 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;
+
if (!xlog_item_is_intent(lip))
break;
@@ -2567,13 +2569,17 @@ 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;
}
}
