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Re: [PATCH] xfs: fix possible NULL dereference

To: "Geyslan G. Bem" <geyslan@xxxxxxxxx>
Subject: Re: [PATCH] xfs: fix possible NULL dereference
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Mon, 21 Oct 2013 15:58:23 -0500
Cc: kernel-br@xxxxxxxxxxxxxxxx, Alex Elder <elder@xxxxxxxxxx>, Ben Myers <bpm@xxxxxxx>, open list <linux-kernel@xxxxxxxxxxxxxxx>, supporter:XFS FILESYSTEM <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1382380366-26540-1-git-send-email-geyslan@xxxxxxxxx>
References: <1382380366-26540-1-git-send-email-geyslan@xxxxxxxxx>
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:17.0) Gecko/20130801 Thunderbird/17.0.8
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@xxxxxxxxxx>

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@xxxxxxxxx>
> ---
>  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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