Re: [PATCH v2] xfs: Fix the free logic of state in xfs_attr_node_hasname

["xuyang2018.jy@fujitsu.com" <xuyang2018.jy@fujitsu.com>]

Hi Darrick, Allison

Any comment?

Best Regards
Yang Xu
> 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 function, xfs_da3_node_lookup_int fails with EFSCORRUPTED in
> xfs_attr_node_hasname because we have use blocktrash to random it in xfs/126. So it
> free state in internal 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 state itself instead of caller if
> xfs_da3_node_lookup_int fails.
> 
> Fix this bug by moving the step of free state into caller.
> 
> Also, use "goto error/out" instead of returning error directly in xfs_attr_node_addname_find_attr and
> xfs_attr_node_removename_setup function because we should free state ourselves.
> 
> Fixes: 07120f1abdff ("xfs: Add xfs_has_attr and subroutines")
> Signed-off-by: Yang Xu<xuyang2018.jy@fujitsu.com>
> ---
>   fs/xfs/libxfs/xfs_attr.c | 17 +++++++----------
>   1 file changed, 7 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index fbc9d816882c..23523b802539 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;
>   }
> 
> @@ -1112,7 +1109,7 @@ xfs_attr_node_addname_find_attr(
>   	 */
>   	retval = xfs_attr_node_hasname(args,&dac->da_state);
>   	if (retval != -ENOATTR&&  retval != -EEXIST)
> -		return retval;
> +		goto error;
> 
>   	if (retval == -ENOATTR&&  (args->attr_flags&  XATTR_REPLACE))
>   		goto error;
> @@ -1337,7 +1334,7 @@ int xfs_attr_node_removename_setup(
> 
>   	error = xfs_attr_node_hasname(args, state);
>   	if (error != -EEXIST)
> -		return error;
> +		goto out;
>   	error = 0;
> 
>   	ASSERT((*state)->path.blk[(*state)->path.active - 1].bp != NULL);