linux-kernel - Re: UBSAN: array-index-out-of-bounds in dbAdjTree

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Date:   Fri, 20 Nov 2020 17:52:36 +0800
From:   butt3rflyh4ck <butterflyhuangxx@...il.com>
To:     Dave Kleikamp <dave.kleikamp@...cle.com>
Cc:     jfs-discussion@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: UBSAN: array-index-out-of-bounds in dbAdjTree

You are welcome and have you submitted the patch to linux upstream ?
If you have no time do that and I can do it.

Regard,
 butt3rflyh4ck.

On Sun, Nov 15, 2020 at 12:17 AM Dave Kleikamp <dave.kleikamp@...cle.com> wrote:
>
> Thanks for reporting and testing this!
>
> Shaggy
>
> On 11/14/20 7:55 AM, butt3rflyh4ck wrote:
> > Yes, I have tested the patch, it seem to fix the problem.
> >
> > Regard,
> >  butt3rflyh4ck.
> >
> > On Sat, Nov 14, 2020 at 5:16 AM Dave Kleikamp <dave.kleikamp@...cle.com> wrote:
> >>
> >> On 10/8/20 12:00 PM, butt3rflyh4ck wrote:
> >>> I report a array-index-out-of-bounds bug (in linux-5.9.0-rc6) found by
> >>> kernel fuzz.
> >>>
> >>> kernel config: https://github.com/butterflyhack/syzkaller-fuzz/blob/master/v5.9.0-rc6-config
> >>>
> >>> and can reproduce.
> >>>
> >>> the dmtree_t is that
> >>> typedef union dmtree {
> >>> struct dmaptree t1;
> >>> struct dmapctl t2;
> >>> } dmtree_t;
> >>>
> >>> the dmaptree is that
> >>> struct dmaptree {
> >>> __le32 nleafs; /* 4: number of tree leafs */
> >>> __le32 l2nleafs; /* 4: l2 number of tree leafs */
> >>> __le32 leafidx; /* 4: index of first tree leaf */
> >>> __le32 height; /* 4: height of the tree */
> >>> s8 budmin; /* 1: min l2 tree leaf value to combine */
> >>> s8 stree[TREESIZE]; /* TREESIZE: tree */
> >>> u8 pad[2]; /* 2: pad to word boundary */
> >>> };
> >>> the TREESIZE is totally 341, but the leafidx type is __le32.
> >>
> >> Does this patch fix the problem?
> >>
> >> jfs: Fix array index bounds check in dbAdjTree
> >>
> >> Bounds checking tools can flag a bug in dbAdjTree() for an array index
> >> out of bounds in dmt_stree. Since dmt_stree can refer to the stree in
> >> both structures dmaptree and dmapctl, use the larger array to eliminate
> >> the false positive.
> >>
> >> Signed-off-by: Dave Kleikamp <dave.kleikamp@...cle.com>
> >> ---
> >>  fs/jfs/jfs_dmap.h | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/fs/jfs/jfs_dmap.h b/fs/jfs/jfs_dmap.h
> >> index 29891fad3f09..aa03a904d5ab 100644
> >> --- a/fs/jfs/jfs_dmap.h
> >> +++ b/fs/jfs/jfs_dmap.h
> >> @@ -183,7 +183,7 @@ typedef union dmtree {
> >>  #define        dmt_leafidx     t1.leafidx
> >>  #define        dmt_height      t1.height
> >>  #define        dmt_budmin      t1.budmin
> >> -#define        dmt_stree       t1.stree
> >> +#define        dmt_stree       t2.stree
> >>
> >>  /*
> >>   *     on-disk aggregate disk allocation map descriptor.
> >> --
> >> 2.29.2
> >>