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

[Jan Kara]

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

> ---
> 
> 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
> 
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR