[PATCH] xfs: Fix the free logic of state in xfs_attr_node_hasname

Yang Xu
2021-10-29T08:52:06Z

When testing xfstests xfs/126 on lastest upstream kernel, it will hang on some machine.
Adding a getxattr operation after xattr corrupted, I can reproduce it 100%.

The deadlock as below:
[983.923403] task:setfattr state:D stack: 0 pid:17639 ppid: 14687 flags:0x00000080
[ 983.923405] Call Trace:
[ 983.923410] __schedule+0x2c4/0x700
[ 983.923412] schedule+0x37/0xa0
[ 983.923414] schedule_timeout+0x274/0x300
[ 983.923416] __down+0x9b/0xf0
[ 983.923451] ? xfs_buf_find.isra.29+0x3c8/0x5f0 [xfs]
[ 983.923453] down+0x3b/0x50
[ 983.923471] xfs_buf_lock+0x33/0xf0 [xfs]
[ 983.923490] xfs_buf_find.isra.29+0x3c8/0x5f0 [xfs]
[ 983.923508] xfs_buf_get_map+0x4c/0x320 [xfs]
[ 983.923525] xfs_buf_read_map+0x53/0x310 [xfs]
[ 983.923541] ? xfs_da_read_buf+0xcf/0x120 [xfs]
[ 983.923560] xfs_trans_read_buf_map+0x1cf/0x360 [xfs]
[ 983.923575] ? xfs_da_read_buf+0xcf/0x120 [xfs]
[ 983.923590] xfs_da_read_buf+0xcf/0x120 [xfs]
[ 983.923606] xfs_da3_node_read+0x1f/0x40 [xfs]
[ 983.923621] xfs_da3_node_lookup_int+0x69/0x4a0 [xfs]
[ 983.923624] ? kmem_cache_alloc+0x12e/0x270
[ 983.923637] xfs_attr_node_hasname+0x6e/0xa0 [xfs]
[ 983.923651] xfs_has_attr+0x6e/0xd0 [xfs]
[ 983.923664] xfs_attr_set+0x273/0x320 [xfs]
[ 983.923683] xfs_xattr_set+0x87/0xd0 [xfs]
[ 983.923686] __vfs_removexattr+0x4d/0x60
[ 983.923688] __vfs_removexattr_locked+0xac/0x130
[ 983.923689] vfs_removexattr+0x4e/0xf0
[ 983.923690] removexattr+0x4d/0x80
[ 983.923693] ? __check_object_size+0xa8/0x16b
[ 983.923695] ? strncpy_from_user+0x47/0x1a0
[ 983.923696] ? getname_flags+0x6a/0x1e0
[ 983.923697] ? _cond_resched+0x15/0x30
[ 983.923699] ? __sb_start_write+0x1e/0x70
[ 983.923700] ? mnt_want_write+0x28/0x50
[ 983.923701] path_removexattr+0x9b/0xb0
[ 983.923702] __x64_sys_removexattr+0x17/0x20
[ 983.923704] do_syscall_64+0x5b/0x1a0
[ 983.923705] entry_SYSCALL_64_after_hwframe+0x65/0xca
[ 983.923707] RIP: 0033:0x7f080f10ee1b

When getxattr calls xfs_attr_node_get, xfs_da3_node_lookup_int fails in
xfs_attr_node_hasname because we have use blocktrash to random it in xfs/126. So it
free stat and xfs_attr_node_get doesn't do xfs_buf_trans release job.

Then subsequent removexattr will hang because of it.

This bug was introduced by kernel commit 07120f1abdff ("xfs: Add xfs_has_attr and subroutines").
It adds xfs_attr_node_hasname helper and said caller will be responsible for freeing the state
in this case. But xfs_attr_node_hasname will free stat itself instead of caller if
xfs_da3_node_lookup_int fails.

Fix this bug by moving the step of free state into caller.

Fixes: 07120f1abdff ("xfs: Add xfs_has_attr and subroutines")
Signed-off-by: Yang Xu <xuyang2018.jy@fujitsu.com>
---
fs/xfs/libxfs/xfs_attr.c | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
index fbc9d816882c..6ad50a76fd8d 100644
--- a/fs/xfs/libxfs/xfs_attr.c
+++ b/fs/xfs/libxfs/xfs_attr.c
@@ -1077,21 +1077,18 @@ xfs_attr_node_hasname(

state = xfs_da_state_alloc(args);
if (statep != NULL)
- *statep = NULL;
+ *statep = state;

/*
* Search to see if name exists, and get back a pointer to it.
*/
error = xfs_da3_node_lookup_int(state, &retval);
- if (error) {
- xfs_da_state_free(state);
- return error;
- }
+ if (error)
+ retval = error;

- if (statep != NULL)
- *statep = state;
- else
+ if (!statep)
xfs_da_state_free(state);
+
return retval;
}

--
2.23.0