[PATCH 5.13 230/351] ubifs: Set/Clear I_LINKABLE under i_lock for whiteout inode

Greg Kroah-Hartman
2021-07-19T17:48:36Z

From: Zhihao Cheng <chengzhihao1@huawei.com>

[ Upstream commit a801fcfeef96702fa3f9b22ad56c5eb1989d9221 ]

xfstests-generic/476 reports a warning message as below:

WARNING: CPU: 2 PID: 30347 at fs/inode.c:361 inc_nlink+0x52/0x70
Call Trace:
do_rename+0x502/0xd40 [ubifs]
ubifs_rename+0x8b/0x180 [ubifs]
vfs_rename+0x476/0x1080
do_renameat2+0x67c/0x7b0
__x64_sys_renameat2+0x6e/0x90
do_syscall_64+0x66/0xe0
entry_SYSCALL_64_after_hwframe+0x44/0xae

Following race case can cause this:
rename_whiteout(Thread 1) wb_workfn(Thread 2)
ubifs_rename
do_rename
__writeback_single_inode
spin_lock(&inode->i_lock)
whiteout->i_state |= I_LINKABLE
inode->i_state &= ~dirty;
---- How race happens on i_state:
(tmp = whiteout->i_state | I_LINKABLE)
(tmp = inode->i_state & ~dirty)
(whiteout->i_state = tmp)
(inode->i_state = tmp)
----
spin_unlock(&inode->i_lock)
inc_nlink(whiteout)
WARN_ON(!(inode->i_state & I_LINKABLE)) !!!

Fix to add i_lock to avoid i_state update race condition.

Fixes: 9e0a1fff8db56ea ("ubifs: Implement RENAME_WHITEOUT")
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/ubifs/dir.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
index 5bd8482e660a..7c61d0ec0159 100644
--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c
@@ -1337,7 +1337,10 @@ static int do_rename(struct inode *old_dir, struct dentry *old_dentry,
goto out_release;
}

+ spin_lock(&whiteout->i_lock);
whiteout->i_state |= I_LINKABLE;
+ spin_unlock(&whiteout->i_lock);
+
whiteout_ui = ubifs_inode(whiteout);
whiteout_ui->data = dev;
whiteout_ui->data_len = ubifs_encode_dev(dev, MKDEV(0, 0));
@@ -1430,7 +1433,11 @@ static int do_rename(struct inode *old_dir, struct dentry *old_dentry,

inc_nlink(whiteout);
mark_inode_dirty(whiteout);
+
+ spin_lock(&whiteout->i_lock);
whiteout->i_state &= ~I_LINKABLE;
+ spin_unlock(&whiteout->i_lock);
+
iput(whiteout);
}

--
2.30.2