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Re: [PATCH V3] xfs_repair: fix agcount*agblocks overflows

To: Eric Sandeen <sandeen@xxxxxxxxxxx>
Subject: Re: [PATCH V3] xfs_repair: fix agcount*agblocks overflows
From: Felix Blyakher <felixb@xxxxxxx>
Date: Thu, 2 Jul 2009 00:24:31 -0500
Cc: xfs-oss <xfs@xxxxxxxxxxx>, Jesse Stroik <jstroik@xxxxxxxxxxxxx>
In-reply-to: <4A4C3407.60501@xxxxxxxxxxx>
References: <4A4BC7FF.6050004@xxxxxxxxxxx> <4A4BE005.3000102@xxxxxxxxxxx> <4A4C3407.60501@xxxxxxxxxxx>

On Jul 1, 2009, at 11:13 PM, Eric Sandeen wrote:

(V3: found another spot with this problem)

The last test in verify_ag_bno() may overflow:

return (agbno >= (sbp->sb_dblocks -
                ((sbp->sb_agcount - 1) * sbp->sb_agblocks)));

because sb_agcount & sb_agblocks are 32-bit integers; this
may then miss corrupt agbnos for the last ag, which can in
turn lead to out of bounds memory accesses later, for example
when the block nr is used to offset in set_agbno_state():

        addr = ba_bmap[(agno)] + (ag_blockno)/XR_BB_NUM;

Similar problems in mk_incore_fstree

Reported-by: Jesse Stroik <jstroik@xxxxxxxxxxxxx>
Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxxx>

Reviewed-by: Felix Blyakher <felixb@xxxxxxx>


---

diff --git a/repair/dinode.c b/repair/dinode.c
index fdf52db..84e1d05 100644
--- a/repair/dinode.c
+++ b/repair/dinode.c
@@ -319,7 +319,8 @@ verify_ag_bno(xfs_sb_t *sbp,
                return (agbno >= sbp->sb_agblocks);
        if (agno == (sbp->sb_agcount - 1))
                return (agbno >= (sbp->sb_dblocks -
-                               ((sbp->sb_agcount - 1) * sbp->sb_agblocks)));
+                               ((xfs_drfsbno_t)(sbp->sb_agcount - 1) *
+                                sbp->sb_agblocks)));
        return 1;
}

diff --git a/repair/phase5.c b/repair/phase5.c
index 2c243b6..77c7363 100644
--- a/repair/phase5.c
+++ b/repair/phase5.c
@@ -113,7 +113,8 @@ mk_incore_fstree(xfs_mount_t *mp, xfs_agnumber_t agno)
                ag_end = mp->m_sb.sb_agblocks;
        else
                ag_end = mp->m_sb.sb_dblocks -
-                       mp->m_sb.sb_agblocks * (mp->m_sb.sb_agcount - 1);
+                       (xfs_drfsbno_t)mp->m_sb.sb_agblocks *
+                        (mp->m_sb.sb_agcount - 1);

        /*
         * ok, now find the number of extents, keep track of the

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