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Re: [PATCH] xfsprogs: fix Out-of-bounds access in repair/dinode.c

To: Ben Myers <bpm@xxxxxxx>
Subject: Re: [PATCH] xfsprogs: fix Out-of-bounds access in repair/dinode.c
From: Li Zhong <zhong@xxxxxxxxxxxxxxxxxx>
Date: Mon, 26 Aug 2013 10:15:27 +0800
Cc: Rich Johnston <rjohnston@xxxxxxx>, Chandra Seetharaman <sekharan@xxxxxxxxxx>, xfsprogs <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20130823163828.GS5262@xxxxxxx>
References: <1376287861.2822.13.camel@ThinkPad-T5421> <5214EFFF.4060105@xxxxxxx> <20130823163828.GS5262@xxxxxxx>
On Fri, 2013-08-23 at 11:38 -0500, Ben Myers wrote:
> Hey Rich and Li Zhong,
> 
> On Wed, Aug 21, 2013 at 11:51:11AM -0500, Rich Johnston wrote:
> > Looks good, thanks for the patch Li Zhong. it has been committed.
> > 
> > --Rich
> > 
> > Reviewed-by: Rich Johnston <rjohnston@xxxxxxx>
> > 
> > commit e7c05095f5baa9cd2e35a6de03d7dd9f51dd3910
> > Author: Li Zhong <zhong@xxxxxxxxxxxxxxxxxx>
> > Date:   Mon Aug 12 06:11:01 2013 +0000
> > 
> >     xfsprogs: fix Out-of-bounds access in repair/dinode.c
> > 
> > On 08/12/2013 01:11 AM, Li Zhong wrote:
> > >Following is reported by coverity in bug 1061528:
> > >
> > >187                        __dirty_no_modify_ret(dirty);
> > >
> > >CID 1061528 (#1 of 1): Out-of-bounds access (OVERRUN)53. 
> > >overrun-buffer-arg: Overrunning array "dinoc->di_pad" of 6 bytes by 
> > >passing it to a function which accesses it at byte offset 15 using 
> > >argument "16UL".
> > >188                        memset(dinoc->di_pad, 0, 16);
> > >
> > >It seems that di_pad here should be di_pad2, as sekharan pointed out.
> > >
> > >Signed-off-by: Li Zhong <zhong@xxxxxxxxxxxxxxxxxx>
> > >---
> > >  repair/dinode.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > >diff --git a/repair/dinode.c b/repair/dinode.c
> > >index e607f0b..94bf2f8 100644
> > >--- a/repair/dinode.c
> > >+++ b/repair/dinode.c
> > >@@ -183,9 +183,9 @@ clear_dinode_core(struct xfs_mount *mp, xfs_dinode_t 
> > >*dinoc, xfs_ino_t ino_num)
> > >   }
> > >
> > >   for (i = 0; i < 16; i++) {
> > >-          if (dinoc->di_pad[i] != 0) {
> > >+          if (dinoc->di_pad2[i] != 0) {
> > >                   __dirty_no_modify_ret(dirty);
> > >-                  memset(dinoc->di_pad, 0, 16);
> > >+                  memset(dinoc->di_pad2, 0, 16);
> > >                   break;
> > >           }
> > >   }
> 
> We also discussed this issue a bit in this thread:
> http://oss.sgi.com/archives/xfs/2013-08/msg00228.html
> 
> Looks like the loop itself is incorrect and should be removed, and Eric has
> suggested that the conditional be changed to a memcmp in case the size of the
> pad changes in the future.  Would either of you care to spin up another patch
> to clean it up?

Hi Ben, 

If I understand correctly, we need to change 16 to be a sizeof the
di_pad2 array(like the fix attached below)? 

It seems to me that the loop is needed to check all of the 16 entries in
the array? 

Thanks, Zhong

---
diff --git a/repair/dinode.c b/repair/dinode.c
index b2b9a95..7469fc8 100644
--- a/repair/dinode.c
+++ b/repair/dinode.c
@@ -182,10 +182,10 @@ clear_dinode_core(struct xfs_mount *mp, xfs_dinode_t 
*dinoc, xfs_ino_t ino_num)
                platform_uuid_copy(&dinoc->di_uuid, &mp->m_sb.sb_uuid);
        }
 
-       for (i = 0; i < 16; i++) {
+       for (i = 0; i < sizeof(dinoc->di_pad2)/sizeof(dinoc->di_pad2[0]); i++) {
                if (dinoc->di_pad2[i] != 0) {
                        __dirty_no_modify_ret(dirty);
-                       memset(dinoc->di_pad2, 0, 16);
+                       memset(dinoc->di_pad2, 0, sizeof(dinoc->di_pad2));
                        break;
                }
        }







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