[Ocfs2-devel] [PATCH RESEND] ocfs2: fix a misuse a of brelse after failing ocfs2_check_dir_entry

[piaojun]

Hi Changwei,

On 2018/5/28 22:40, Changwei Ge wrote:
> From: Changwei Ge <ge.changwei at h3c.com>
> 
> Somehow, file system metadata was corrupted, which causes
> ocfs2_check_dir_entry() to fail in function ocfs2_dir_foreach_blk_el().
> 
> According to the original design intention, if above happens we should
> skip the problematic block and continue to retrieve dir entry. But there
> is obviouse misuse of brelse around related code.
> 
> After failure of ocfs2_check_dir_entry(), currunt code just moves to next
> position and uses the problematic buffer head again and again during
> which the problematic buffer head is released for multiple times. I
> suppose, this a serious issue which is long-lived in ocfs2. This may
> cause other file systems which is also used in a the same host insane.
> 
> So we should also consider about bakcporting this patch into
> linux -stable.
> 
> Suggested-by: Changkuo Shi <shi.changkuo at h3c.com>
> Cc: stable at vger.kernel.org
> Signed-off-by: Changwei Ge <ge.changwei at h3c.com>
> ---
>  fs/ocfs2/dir.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/ocfs2/dir.c b/fs/ocfs2/dir.c
> index b048d4f..c121abb 100644
> --- a/fs/ocfs2/dir.c
> +++ b/fs/ocfs2/dir.c
> @@ -1897,8 +1897,7 @@ static int ocfs2_dir_foreach_blk_el(struct inode *inode,
>  				/* On error, skip the f_pos to the
>  				   next block. */
>  				ctx->pos = (ctx->pos | (sb->s_blocksize - 1)) + 1;
> -				brelse(bh);
> -				continue;
> +				break;

I guess return is more appropriate than break here as it will cause double
free buffer:

"
ctx->pos = (ctx->pos | (sb->s_blocksize - 1)) + 1;
brelse(bh);
break;
"

"
brelse(bh);
bh = NULL;
if (!persist && stored)
	break;
"

Thanks,
Jun

>  			}
>  			if (le64_to_cpu(de->inode)) {
>  				unsigned char d_type = DT_UNKNOWN;
>