From: Shigeru Yoshida <syoshida@xxxxxxxxxx> [ 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@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Shigeru Yoshida <syoshida@xxxxxxxxxx> Signed-off-by: Jan Kara <jack@xxxxxxx> Link: https://lore.kernel.org/r/20221023095741.271430-1-syoshida@xxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- 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 aefa939176e1..0ab842460ed3 100644 --- a/fs/udf/namei.c +++ b/fs/udf/namei.c @@ -1112,8 +1112,9 @@ static int udf_rename(struct inode *old_dir, struct dentry *old_dentry, 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; } @@ -1122,8 +1123,7 @@ static int udf_rename(struct inode *old_dir, struct dentry *old_dentry, 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
