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

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

Posted by Gianfranco Trad 1 year, 4 months ago

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>
---

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

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

Posted by Jan Kara 1 year, 4 months ago

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

> ---
> 
> 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
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

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

Posted by Gianfranco Trad 1 year, 4 months ago

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
>>