linux-kernel - Re: [PATCH] jfs: fix array-index-out-of-bounds in dbFindLeaf

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Message-ID: <ae6ce935-96eb-3d40-f252-54fff7eb0ea9@gmail.com>
Date:   Thu, 31 Aug 2023 20:49:09 +0530
From:   Manas Ghandat <ghandatmanas@...il.com>
To:     Dave Kleikamp <dave.kleikamp@...cle.com>, shaggy@...nel.org,
        liushixin2@...wei.com
Cc:     linux-kernel@...r.kernel.org, jfs-discussion@...ts.sourceforge.net,
        Linux-kernel-mentees@...ts.linuxfoundation.org,
        syzbot+aea1ad91e854d0a83e04@...kaller.appspotmail.com
Subject: Re: [PATCH] jfs: fix array-index-out-of-bounds in dbFindLeaf

I was wondering if we could implement a get_tree_size macro wherein  we 
could find the tree size so that we can do the comparison. SInce the 
tp->dmt_stree is an array we can get its size and fix the out of bounds. 
Would this thing work?

On 30/08/23 00:08, Dave Kleikamp wrote:
> This won't work. dbFindLeaf() can be called from dbFindCtl() with 
> struct dmapctl whose stree index can be as high as CTLTREESIZE which 
> is larger than TREESIZE. A check against CTLTREESIZE might be better 
> than nothing at all but won't necessarily detect an overflow. 
> Currently, dbFindLeaf doesn't have anything to tell it which tree it 
> is working on.
>
> We could pass in the treesize as an argument to dbFindCtl() if we 
> can't come up with something simpler.
>
> Shaggy
>
>>
>> Signed-off-by: Manas Ghandat <ghandatmanas@...il.com>
>> Reported-by: syzbot+aea1ad91e854d0a83e04@...kaller.appspotmail.com
>> Closes: https://syzkaller.appspot.com/bug?extid=aea1ad91e854d0a83e04
>> ---
>>   fs/jfs/jfs_dmap.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
>> index a14a0f18a4c4..5af17b2287be 100644
>> --- a/fs/jfs/jfs_dmap.c
>> +++ b/fs/jfs/jfs_dmap.c
>> @@ -2948,6 +2948,10 @@ static int dbFindLeaf(dmtree_t * tp, int l2nb, 
>> int *leafidx)
>>               /* sufficient free space found.  move to the next
>>                * level (or quit if this is the last level).
>>                */
>> +
>> +            if (x + n > TREESIZE)
>> +                return -ENOSPC;
>> +
>>               if (l2nb <= tp->dmt_stree[x + n])
>>                   break;
>>           }