Re: [PATCH] jfs: fix shift-out-of-bounds in dbJoin

[Dave Kleikamp <dave.kleikamp@oracle.com>]

On 10/11/23 9:39AM, Manas Ghandat wrote:
> Currently while joining the leaf in a buddy system there is shift out
> of bound error in calculation of BUDSIZE. Added the required check
> to the BUDSIZE and fixed the documentation as well.

Looks good.

Thanks,
Shaggy

> 
> Reported-by: syzbot+411debe54d318eaed386@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=411debe54d318eaed386
> Signed-off-by: Manas Ghandat <ghandatmanas@gmail.com>
> ---
>   fs/jfs/jfs_dmap.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
> index 6b838d3ae7c2..baa97bda1c7a 100644
> --- a/fs/jfs/jfs_dmap.c
> +++ b/fs/jfs/jfs_dmap.c
> @@ -2730,7 +2730,9 @@ static int dbBackSplit(dmtree_t * tp, int leafno)
>    *	leafno	- the number of the leaf to be updated.
>    *	newval	- the new value for the leaf.
>    *
> - * RETURN VALUES: none
> + * RETURN VALUES:
> + *  0		- success
> + *	-EIO	- i/o error
>    */
>   static int dbJoin(dmtree_t * tp, int leafno, int newval)
>   {
> @@ -2757,6 +2759,10 @@ static int dbJoin(dmtree_t * tp, int leafno, int newval)
>   		 * get the buddy size (number of words covered) of
>   		 * the new value.
>   		 */
> +
> +		if ((newval - tp->dmt_budmin) > BUDMIN)
> +			return -EIO;
> +
>   		budsz = BUDSIZE(newval, tp->dmt_budmin);
>   
>   		/* try to join.