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

Darrick J. Wong
2021-11-17T01:58:12Z

On Mon, Nov 15, 2021 at 01:27:28AM +0000, xuyang2018.jy@fujitsu.com wrote:
> on 2021/11/5 11:12, xuyang2018.jy@fujitsu.com wrote:
> > Hi Darrick, Allison
> >
> > Any comment?
> Ping.

FWIW I think it looks fine, but I was kinda wondering if Allison had any
input?

--D

> >
> > 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);
> >
> >