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

[Gianfranco Trad <gianf.trad@gmail.com>]

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@syzkaller.appspotmail.com
>> Closes: https://syzkaller.appspot.com/bug?extid=8901c4560b7ab5c2f9df
>> Tested-by: syzbot+8901c4560b7ab5c2f9df@syzkaller.appspotmail.com
>> Suggested-by: Jan Kara <jack@suse.com>
>> Signed-off-by: Gianfranco Trad <gianf.trad@gmail.com>
> 
> 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@gmail.com/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
>>