linux-kernel - Re: [PATCH] ocfs2: remove unreasonable unlock

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Message-ID: <2e662cb6-47d9-4bbd-855d-1f6d5edb8633@suse.com>
Date: Tue, 20 Aug 2024 12:04:39 +0800
From: "heming.zhao@...e.com" <heming.zhao@...e.com>
To: Lizhi Xu <lizhi.xu@...driver.com>, joseph.qi@...ux.alibaba.com,
 syzbot+ab134185af9ef88dfed5@...kaller.appspotmail.com
Cc: jlbec@...lplan.org, linux-kernel@...r.kernel.org, mark@...heh.com,
 ocfs2-devel@...ts.linux.dev, syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] ocfs2: remove unreasonable unlock



On 8/19/24 10:51, Lizhi Xu wrote:
> There was a lock release before exiting, so remove the unreasonable unlock.
> 
> Reported-and-tested-by: syzbot+ab134185af9ef88dfed5@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=ab134185af9ef88dfed5
> Signed-off-by: Lizhi Xu <lizhi.xu@...driver.com>
> ---
>   fs/ocfs2/buffer_head_io.c | 1 -
>   1 file changed, 1 deletion(-)
> 
> diff --git a/fs/ocfs2/buffer_head_io.c b/fs/ocfs2/buffer_head_io.c
> index cdb9b9bdea1f..e62c7e1de4eb 100644
> --- a/fs/ocfs2/buffer_head_io.c
> +++ b/fs/ocfs2/buffer_head_io.c
> @@ -235,7 +235,6 @@ int ocfs2_read_blocks(struct ocfs2_caching_info *ci, u64 block, int nr,
>   		if (bhs[i] == NULL) {
>   			bhs[i] = sb_getblk(sb, block++);
>   			if (bhs[i] == NULL) {
> -				ocfs2_metadata_cache_io_unlock(ci);
>   				status = -ENOMEM;
>   				mlog_errno(status);
>   				/* Don't forget to put previous bh! */

The fix looks good to me. However, I found another issue in this function.

In the for-loop after the 'read_failure' label, the condition
'(bh == NULL) && flags includes OCFS2_BH_READAHEAD' is missing.
When this contidion is true, this for-loop will call ocfs2_set_buffer_uptodate(ci, bh),
which then triggers a NULL pointer access error.

If you agree with my analysis, please add the new fix and send a v2 patch.

Thanks,
Heming