Re: [PATCH v2] udf: fix uninit-value use in udf_get_fileshortad

[Gianfranco Trad]

On 02/10/24 14:29, Jan Kara wrote:
> On Wed 25-09-24 09:46:15, Gianfranco Trad wrote:
> > Check for overflow when computing alen in udf_current_aext to mitigate
> > later uninit-value use in udf_get_fileshortad KMSAN bug[1].
> > After applying the patch reproducer did not trigger any issue[2].
> >
> > [1] https://syzkaller.appspot.com/bug?extid=8901c4560b7ab5c2f9df
> > [2] https://syzkaller.appspot.com/x/log.txt?x=10242227980000
> >
> > Reported-by: syzbot+8901c4560b7ab5c2f9df@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Closes: https://syzkaller.appspot.com/bug?extid=8901c4560b7ab5c2f9df
> > Tested-by: syzbot+8901c4560b7ab5c2f9df@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Suggested-by: Jan Kara <jack@xxxxxxxx>
> > Signed-off-by: Gianfranco Trad <gianf.trad@xxxxxxxxx>
>
> Thanks. I've added the patch to my tree.
>
> 								Honza

Thanks Jan. This was one of my first patches to the kernel. I will 
definitely remember it. Wish you a nice day :)

-- Gian

> > ---
> >
> > Notes:
> > 	changes in v2:
> > 		- use check_add_overflow helper to check for overflow.
> > 	
> > 	link to v1: https://lore.kernel.org/all/20240919195227.412583-1-gianf.trad@xxxxxxxxx/T/
> >
> >   fs/udf/inode.c | 7 ++++---
> >   1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/udf/inode.c b/fs/udf/inode.c
> > index 4726a4d014b6..811a035b600f 100644
> > --- a/fs/udf/inode.c
> > +++ b/fs/udf/inode.c
> > @@ -2215,9 +2215,10 @@ int8_t udf_current_aext(struct inode *inode, struct extent_position *epos,
> >   		if (!epos->offset)
> >   			epos->offset = sizeof(struct allocExtDesc);
> >   		ptr = epos->bh->b_data + epos->offset;
> > -		alen = sizeof(struct allocExtDesc) +
> > -			le32_to_cpu(((struct allocExtDesc *)epos->bh->b_data)->
> > -							lengthAllocDescs);
> > +		if (check_add_overflow(sizeof(struct allocExtDesc),
> > +					le32_to_cpu(((struct allocExtDesc *)epos->bh->b_data)
> > +						->lengthAllocDescs), &alen))
> > +			return -1;
> >   	}
> >   
> >   	switch (iinfo->i_alloc_type) {
> > --
> > 2.43.0