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Subject[PATCH AUTOSEL 6.0 02/16] udf: Avoid double brelse() in udf_rename()
Date
From: Shigeru Yoshida <syoshida@redhat.com>

[ Upstream commit c791730f2554a9ebb8f18df9368dc27d4ebc38c2 ]

syzbot reported a warning like below [1]:

VFS: brelse: Trying to free free buffer
WARNING: CPU: 2 PID: 7301 at fs/buffer.c:1145 __brelse+0x67/0xa0
...
Call Trace:
<TASK>
invalidate_bh_lru+0x99/0x150
smp_call_function_many_cond+0xe2a/0x10c0
? generic_remap_file_range_prep+0x50/0x50
? __brelse+0xa0/0xa0
? __mutex_lock+0x21c/0x12d0
? smp_call_on_cpu+0x250/0x250
? rcu_read_lock_sched_held+0xb/0x60
? lock_release+0x587/0x810
? __brelse+0xa0/0xa0
? generic_remap_file_range_prep+0x50/0x50
on_each_cpu_cond_mask+0x3c/0x80
blkdev_flush_mapping+0x13a/0x2f0
blkdev_put_whole+0xd3/0xf0
blkdev_put+0x222/0x760
deactivate_locked_super+0x96/0x160
deactivate_super+0xda/0x100
cleanup_mnt+0x222/0x3d0
task_work_run+0x149/0x240
? task_work_cancel+0x30/0x30
do_exit+0xb29/0x2a40
? reacquire_held_locks+0x4a0/0x4a0
? do_raw_spin_lock+0x12a/0x2b0
? mm_update_next_owner+0x7c0/0x7c0
? rwlock_bug.part.0+0x90/0x90
? zap_other_threads+0x234/0x2d0
do_group_exit+0xd0/0x2a0
__x64_sys_exit_group+0x3a/0x50
do_syscall_64+0x34/0xb0
entry_SYSCALL_64_after_hwframe+0x63/0xcd

The cause of the issue is that brelse() is called on both ofibh.sbh
and ofibh.ebh by udf_find_entry() when it returns NULL. However,
brelse() is called by udf_rename(), too. So, b_count on buffer_head
becomes unbalanced.

This patch fixes the issue by not calling brelse() by udf_rename()
when udf_find_entry() returns NULL.

Link: https://syzkaller.appspot.com/bug?id=8297f45698159c6bca8a1f87dc983667c1a1c851 [1]
Reported-by: syzbot+7902cd7684bc35306224@syzkaller.appspotmail.com
Signed-off-by: Shigeru Yoshida <syoshida@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20221023095741.271430-1-syoshida@redhat.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/udf/namei.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/udf/namei.c b/fs/udf/namei.c
index 865e658535b1..0e30a50060d9 100644
--- a/fs/udf/namei.c
+++ b/fs/udf/namei.c
@@ -1091,8 +1091,9 @@ static int udf_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
return -EINVAL;

ofi = udf_find_entry(old_dir, &old_dentry->d_name, &ofibh, &ocfi);
- if (IS_ERR(ofi)) {
- retval = PTR_ERR(ofi);
+ if (!ofi || IS_ERR(ofi)) {
+ if (IS_ERR(ofi))
+ retval = PTR_ERR(ofi);
goto end_rename;
}

@@ -1101,8 +1102,7 @@ static int udf_rename(struct user_namespace *mnt_userns, struct inode *old_dir,

brelse(ofibh.sbh);
tloc = lelb_to_cpu(ocfi.icb.extLocation);
- if (!ofi || udf_get_lb_pblock(old_dir->i_sb, &tloc, 0)
- != old_inode->i_ino)
+ if (udf_get_lb_pblock(old_dir->i_sb, &tloc, 0) != old_inode->i_ino)
goto end_rename;

nfi = udf_find_entry(new_dir, &new_dentry->d_name, &nfibh, &ncfi);
--
2.35.1
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