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

[Manas Ghandat <ghandatmanas@gmail.com>]

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@gmail.com>
>> Reported-by: syzbot+aea1ad91e854d0a83e04@syzkaller.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;
>>           }