On 2022/11/8 1:13, Darrick J. Wong wrote:
On Mon, Nov 07, 2022 at 10:27:15PM +0800, Guo Xuenan wrote:
Fix uaf in xfs_trans_ail_delete during xlog force shutdown.
In commit cd6f79d1fb32 ("xfs: run callbacks before waking waiters in
xlog_state_shutdown_callbacks") changed the order of running callbacks
and wait for iclog completion to avoid unmount path untimely destroy AIL.
But which seems not enough to ensue this, adding mdelay in
`xfs_buf_item_unpin` can prove that.
The reproduction is as follows. To ensure destroy AIL safely,
we should wait all xlog ioend workers done and sync the AIL.
==================================================================
BUG: KASAN: use-after-free in xfs_trans_ail_delete+0x240/0x2a0
Read of size 8 at addr ffff888023169400 by task kworker/1:1H/43
CPU: 1 PID: 43 Comm: kworker/1:1H Tainted: G W
6.1.0-rc1-00002-gc28266863c4a #137
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.13.0-1ubuntu1.1 04/01/2014
Workqueue: xfs-log/sda xlog_ioend_work
Call Trace:
<TASK>
dump_stack_lvl+0x4d/0x66
print_report+0x171/0x4a6
kasan_report+0xb3/0x130
xfs_trans_ail_delete+0x240/0x2a0
xfs_buf_item_done+0x7b/0xa0
xfs_buf_ioend+0x1e9/0x11f0
xfs_buf_item_unpin+0x4c8/0x860
xfs_trans_committed_bulk+0x4c2/0x7c0
xlog_cil_committed+0xab6/0xfb0
xlog_cil_process_committed+0x117/0x1e0
xlog_state_shutdown_callbacks+0x208/0x440
xlog_force_shutdown+0x1b3/0x3a0
xlog_ioend_work+0xef/0x1d0
process_one_work+0x6f9/0xf70
worker_thread+0x578/0xf30
kthread+0x28c/0x330
ret_from_fork+0x1f/0x30
</TASK>
Allocated by task 9606:
kasan_save_stack+0x1e/0x40
kasan_set_track+0x21/0x30
__kasan_kmalloc+0x7a/0x90
__kmalloc+0x59/0x140
kmem_alloc+0xb2/0x2f0
xfs_trans_ail_init+0x20/0x320
xfs_log_mount+0x37e/0x690
xfs_mountfs+0xe36/0x1b40
xfs_fs_fill_super+0xc5c/0x1a70
get_tree_bdev+0x3c5/0x6c0
vfs_get_tree+0x85/0x250
path_mount+0xec3/0x1830
do_mount+0xef/0x110
__x64_sys_mount+0x150/0x1f0
do_syscall_64+0x35/0x80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
Freed by task 9662:
kasan_save_stack+0x1e/0x40
kasan_set_track+0x21/0x30
kasan_save_free_info+0x2a/0x40
__kasan_slab_free+0x105/0x1a0
__kmem_cache_free+0x99/0x2d0
kvfree+0x3a/0x40
xfs_log_unmount+0x60/0xf0
xfs_unmountfs+0xf3/0x1d0
xfs_fs_put_super+0x78/0x300
generic_shutdown_super+0x151/0x400
kill_block_super+0x9a/0xe0
deactivate_locked_super+0x82/0xe0
deactivate_super+0x91/0xb0
cleanup_mnt+0x32a/0x4a0
task_work_run+0x15f/0x240
exit_to_user_mode_prepare+0x188/0x190
syscall_exit_to_user_mode+0x12/0x30
do_syscall_64+0x42/0x80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
The buggy address belongs to the object at ffff888023169400
which belongs to the cache kmalloc-128 of size 128
The buggy address is located 0 bytes inside of
128-byte region [ffff888023169400, ffff888023169480)
The buggy address belongs to the physical page:
page:ffffea00008c5a00 refcount:1 mapcount:0 mapping:0000000000000000
index:0xffff888023168f80 pfn:0x23168
head:ffffea00008c5a00 order:1 compound_mapcount:0 compound_pincount:0
flags: 0x1fffff80010200(slab|head|node=0|zone=1|lastcpupid=0x1fffff)
raw: 001fffff80010200 ffffea00006b3988 ffffea0000577a88 ffff88800f842ac0
raw: ffff888023168f80 0000000000150007 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff888023169300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888023169380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888023169400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888023169480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888023169500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
Disabling lock debugging due to kernel taint
Fixes: cd6f79d1fb32 ("xfs: run callbacks before waking waiters in xlog_state_shutdown_callbacks")
Signed-off-by: Guo Xuenan <guoxuenan@xxxxxxxxxx>
---
fs/xfs/xfs_log.c | 33 ++++++++++++++++++++++-----------
1 file changed, 22 insertions(+), 11 deletions(-)
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index f02a0dd522b3..89fcd2b8cdfc 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -82,6 +82,9 @@ STATIC int
xlog_iclogs_empty(
struct xlog *log);
+static void
+xlog_wait_iodone(struct xlog *log);
+
static int
xfs_log_cover(struct xfs_mount *);
@@ -886,6 +889,23 @@ xlog_force_iclog(
return xlog_state_release_iclog(iclog->ic_log, iclog, NULL);
}
+/*
+ * Cycle all the iclogbuf locks to make sure all log IO completion
+ * is done before we tear down AIL/CIL.
+ */
+static void
+xlog_wait_iodone(struct xlog *log)
It's ok to have pulled this into a helper function, but to repeat a
question from v1: why shouldn't this be done as part of xfs_log_quiesce?
Is there a particular reason why we *don't* want to wait for log IO
completions as part of a freeze? I guess that's because a frozen dead
filesystem still has all the incore state, so log IO completion work
racing with the freeze isn't a big deal?
yes, you're right, as you guess, I thought the umount process need to
wait xlog
io compeletion, and fix it not affecting other path (xfs freeze).But, as
you pointed
out, I think put this into xfs_log_quiesce have no problem.I will resend
v3 laterly
+{
+ int i;
+ xlog_in_core_t *iclog = log->l_iclog;
Nit: Please use 'struct xlog_in_core', not the typedefs.
Ok, will fix it.
+
+ for (i = 0; i < log->l_iclog_bufs; i++) {
+ down(&iclog->ic_sema);
+ up(&iclog->ic_sema);
+ iclog = iclog->ic_next;
+ }
+}
+
/*
* Wait for the iclog and all prior iclogs to be written disk as required by the
* log force state machine. Waiting on ic_force_wait ensures iclog completions
@@ -1095,6 +1115,7 @@ xfs_log_clean(
struct xfs_mount *mp)
{
xfs_log_quiesce(mp);
+ xlog_wait_iodone(mp->m_log);
Wherever you inject this callsite, it needs a comment stating /why/ it's
necessary to wait for the iclog completions even after a log force and
xfs_ail_push_all_sync call.
OK,comments will be added.
Best regards,
Xuenan.
--D
xfs_log_unmount_write(mp);
}
@@ -2113,17 +2134,7 @@ xlog_dealloc_log(
xlog_in_core_t *iclog, *next_iclog;
int i;
- /*
- * Cycle all the iclogbuf locks to make sure all log IO completion
- * is done before we tear down these buffers.
- */
- iclog = log->l_iclog;
- for (i = 0; i < log->l_iclog_bufs; i++) {
- down(&iclog->ic_sema);
- up(&iclog->ic_sema);
- iclog = iclog->ic_next;
- }
-
+ xlog_wait_iodone(log);
/*
* Destroy the CIL after waiting for iclog IO completion because an
* iclog EIO error will try to shut down the log, which accesses the
--
2.31.1
.
--
Guo Xuenan [OS Kernel Lab]
-----------------------------
Email: guoxuenan@xxxxxxxxxx
