block: Fix wrong offset in bio_truncate()

[PATCH] block: Fix wrong offset in bio_truncate()

Posted by OGAWA Hirofumi 4 years, 5 months ago

bio_truncate() clears the buffer outside of last block of bdev, however
current bio_truncate() is using the wrong offset of page. So it can
return the uninitialized data.

This happened when both of truncated/corrupted FS and userspace (via
bdev) are trying to read the last of bdev.

Reported-by: syzbot+ac94ae5f68b84197f41c@syzkaller.appspotmail.com
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
---
 block/bio.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/bio.c b/block/bio.c
index a6fb6a0..25f1ed2 100644
--- a/block/bio.c	2021-11-01 09:19:05.999472589 +0900
+++ b/block/bio.c	2022-01-09 17:40:09.010438012 +0900
@@ -567,7 +567,8 @@ void bio_truncate(struct bio *bio, unsig
 				offset = new_size - done;
 			else
 				offset = 0;
-			zero_user(bv.bv_page, offset, bv.bv_len - offset);
+			zero_user(bv.bv_page, bv.bv_offset + offset,
+				  bv.bv_len - offset);
 			truncated = true;
 		}
 		done += bv.bv_len;
_

-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

Re: [PATCH] block: Fix wrong offset in bio_truncate()

Posted by Ming Lei 4 years, 5 months ago

On Sun, Jan 09, 2022 at 06:36:43PM +0900, OGAWA Hirofumi wrote:
> bio_truncate() clears the buffer outside of last block of bdev, however
> current bio_truncate() is using the wrong offset of page. So it can
> return the uninitialized data.
> 
> This happened when both of truncated/corrupted FS and userspace (via
> bdev) are trying to read the last of bdev.
> 
> Reported-by: syzbot+ac94ae5f68b84197f41c@syzkaller.appspotmail.com
> Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
> ---
>  block/bio.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/block/bio.c b/block/bio.c
> index a6fb6a0..25f1ed2 100644
> --- a/block/bio.c	2021-11-01 09:19:05.999472589 +0900
> +++ b/block/bio.c	2022-01-09 17:40:09.010438012 +0900
> @@ -567,7 +567,8 @@ void bio_truncate(struct bio *bio, unsig
>  				offset = new_size - done;
>  			else
>  				offset = 0;
> -			zero_user(bv.bv_page, offset, bv.bv_len - offset);
> +			zero_user(bv.bv_page, bv.bv_offset + offset,
> +				  bv.bv_len - offset);

Looks correct:

Reviewed-by: Ming Lei <ming.lei@redhat.com>

-- 
Ming

Re: [PATCH] block: Fix wrong offset in bio_truncate()

Posted by OGAWA Hirofumi 4 years, 5 months ago

Ming Lei <ming.lei@redhat.com> writes:

> On Sun, Jan 09, 2022 at 06:36:43PM +0900, OGAWA Hirofumi wrote:
>> bio_truncate() clears the buffer outside of last block of bdev, however
>> current bio_truncate() is using the wrong offset of page. So it can
>> return the uninitialized data.
>> 
>> This happened when both of truncated/corrupted FS and userspace (via
>> bdev) are trying to read the last of bdev.
>> 
>> Reported-by: syzbot+ac94ae5f68b84197f41c@syzkaller.appspotmail.com
>> Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
>> ---
>>  block/bio.c |    3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>> 
>> diff --git a/block/bio.c b/block/bio.c
>> index a6fb6a0..25f1ed2 100644
>> --- a/block/bio.c	2021-11-01 09:19:05.999472589 +0900
>> +++ b/block/bio.c	2022-01-09 17:40:09.010438012 +0900
>> @@ -567,7 +567,8 @@ void bio_truncate(struct bio *bio, unsig
>>  				offset = new_size - done;
>>  			else
>>  				offset = 0;
>> -			zero_user(bv.bv_page, offset, bv.bv_len - offset);
>> +			zero_user(bv.bv_page, bv.bv_offset + offset,
>> +				  bv.bv_len - offset);
>
> Looks correct:
>
> Reviewed-by: Ming Lei <ming.lei@redhat.com>

ping?
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

Re: [PATCH] block: Fix wrong offset in bio_truncate()

Posted by Jens Axboe 4 years, 5 months ago

On Sun, 09 Jan 2022 18:36:43 +0900, OGAWA Hirofumi wrote:
> bio_truncate() clears the buffer outside of last block of bdev, however
> current bio_truncate() is using the wrong offset of page. So it can
> return the uninitialized data.
> 
> This happened when both of truncated/corrupted FS and userspace (via
> bdev) are trying to read the last of bdev.
> 
> [...]

Applied, thanks!

[1/1] block: Fix wrong offset in bio_truncate()
      commit: 3ee859e384d453d6ac68bfd5971f630d9fa46ad3

Best regards,
-- 
Jens Axboe