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Re: [PATCH] xfs: superblock buffers need to be sector sized

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH] xfs: superblock buffers need to be sector sized
From: Brian Foster <bfoster@xxxxxxxxxx>
Date: Tue, 24 Feb 2015 08:36:52 -0500
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1424761944-2034-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1424761944-2034-1-git-send-email-david@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.23 (2014-03-12)
On Tue, Feb 24, 2015 at 06:12:24PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
> 
> In secondary_sb_wack() we zero the unused portion of both the
> on-disk superblock and the in-memory copy that we have. When
> the device sector size is 4k, this causes xfs_repair to crash like
> so:
> 
> # xfs_repair /dev/ram1
> Phase 1 - find and verify superblock...
> Phase 2 - using internal log
>         - zero log...
>         - scan filesystem freespace and inode maps...
> bad magic number
> bad on-disk superblock 3 - bad magic number
> primary/secondary superblock 3 conflict - AG superblock geometry info 
> conflicts with filesystem geometry
> zeroing unused portion of secondary superblock (AG #3)
> #
> 
> The stack trace is indicative:
> 
> #0  memset ()
> #1  0x000000000040404b in secondary_sb_wack
> #2  verify_set_agheader
> #3  0x0000000000427b4b in scan_ag
> #4  0x000000000042a2ca in worker_thread
> #5  0x00007ffff77ba0a4 in start_thread
> #6  0x00007ffff74efc2d in clone
> 
> Which points at memset overrunning the in memory buffer, as it is
> only 512 bytes in length.
> 
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> ---

The patch subject line should probably say 'xfsprogs:' or 'repair:,'
otherwise this looks good to me:

Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>

>  repair/scan.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/repair/scan.c b/repair/scan.c
> index ce8d7f5..12aa782 100644
> --- a/repair/scan.c
> +++ b/repair/scan.c
> @@ -1485,7 +1485,7 @@ scan_ag(
>       int             status;
>       char            *objname = NULL;
>  
> -     sb = (struct xfs_sb *)calloc(BBSIZE, 1);
> +     sb = (struct xfs_sb *)calloc(BBTOB(XFS_FSS_TO_BB(mp, 1)), 1);
>       if (!sb) {
>               do_error(_("can't allocate memory for superblock\n"));
>               return;
> -- 
> 2.0.0
> 
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