Re: [PATCH] xfs: fix possible NULL dereference

From: Eric Sandeen <sandeen@sandeen.net>
To: "Geyslan G. Bem" <geyslan@gmail.com>
Cc: Ben Myers <bpm@sgi.com>, Alex Elder <elder@kernel.org>,
	open list <linux-kernel@vger.kernel.org>,
	kernel-br@googlegroups.com, XFS FILESYSTEM <xfs@oss.sgi.com>
Subject: Re: [PATCH] xfs: fix possible NULL dereference
Date: Mon, 21 Oct 2013 15:58:23 -0500	[thread overview]
Message-ID: <5265956F.4010700@sandeen.net> (raw)
In-Reply-To: <1382380366-26540-1-git-send-email-geyslan@gmail.com>

On 10/21/13 1:32 PM, Geyslan G. Bem wrote:
> This patch puts a 'break' in the true branch, avoiding the 'icptr->ic_next'
> dereferencing.

Reviewed-by: Eric Sandeen <sandeen@redhat.com>

Hm, yeah - cmn_err(CE_PANIC, " " ); used to BUG_ON, but the newer
xfs_emerg() doesn't.

Dave, was that intentional?

I wonder if there are more spots after xfs_emerg()'s which aren't
defensive, because the code used to just panic there.

-Eric

> Signed-off-by: Geyslan G. Bem <geyslan@gmail.com>
> ---
>  fs/xfs/xfs_log.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index a2dea108..8cdeb7e 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
> @@ -3703,8 +3703,10 @@ xlog_verify_iclog(
>  	spin_lock(&log->l_icloglock);
>  	icptr = log->l_iclog;
>  	for (i=0; i < log->l_iclog_bufs; i++) {
> -		if (icptr == NULL)
> +		if (!icptr) {
>  			xfs_emerg(log->l_mp, "%s: invalid ptr", __func__);
> +			break;
> +		}
>  		icptr = icptr->ic_next;
>  	}
>  	if (icptr != log->l_iclog)
> 

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