On 15/04/2021 18:37, Pavel Begunkov wrote:
> On 09/04/2021 15:49, Pavel Begunkov wrote:
>> On 01/04/2021 08:18, yangerkun wrote:
>>> We get a bug:
>>>
>>> BUG: KASAN: slab-out-of-bounds in iov_iter_revert+0x11c/0x404
>>> lib/iov_iter.c:1139
>>> Read of size 8 at addr ffff0000d3fb11f8 by task
>>>
>>> CPU: 0 PID: 12582 Comm: syz-executor.2 Not tainted
>>> 5.10.0-00843-g352c8610ccd2 #2
>>> Hardware name: linux,dummy-virt (DT)
>>> Call trace:
> ...
>>> __asan_load8+0xb4/0xbc mm/kasan/generic.c:252
>>> iov_iter_revert+0x11c/0x404 lib/iov_iter.c:1139
>>> io_read fs/io_uring.c:3421 [inline]
>>> io_issue_sqe+0x2344/0x2d64 fs/io_uring.c:5943
>>> __io_queue_sqe+0x19c/0x520 fs/io_uring.c:6260
>>> io_queue_sqe+0x2a4/0x590 fs/io_uring.c:6326
>>> io_submit_sqe fs/io_uring.c:6395 [inline]
>>> io_submit_sqes+0x4c0/0xa04 fs/io_uring.c:6624
> ...
>>>
>>> blkdev_read_iter can truncate iov_iter's count since the count + pos may
>>> exceed the size of the blkdev. This will confuse io_read that we have
>>> consume the iovec. And once we do the iov_iter_revert in io_read, we
>>> will trigger the slab-out-of-bounds. Fix it by reexpand the count with
>>> size has been truncated.
>>
>> Looks right,
>>
>> Acked-by: Pavel Begunkov <asml.silencec@xxxxxxxxx>
>
> Fwiw, we need to forget to drag it through 5.13 + stable
Err, yypo, to _not_ forget to 5.13 + stable...
>
>
>>>
>>> blkdev_write_iter can trigger the problem too.
>>>
>>> Signed-off-by: yangerkun <yangerkun@xxxxxxxxxx>
>>> ---
>>> fs/block_dev.c | 20 +++++++++++++++++---
>>> 1 file changed, 17 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/fs/block_dev.c b/fs/block_dev.c
>>> index 92ed7d5df677..788e1014576f 100644
>>> --- a/fs/block_dev.c
>>> +++ b/fs/block_dev.c
>>> @@ -1680,6 +1680,7 @@ ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
>>> struct inode *bd_inode = bdev_file_inode(file);
>>> loff_t size = i_size_read(bd_inode);
>>> struct blk_plug plug;
>>> + size_t shorted = 0;
>>> ssize_t ret;
>>>
>>> if (bdev_read_only(I_BDEV(bd_inode)))
>>> @@ -1697,12 +1698,17 @@ ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
>>> if ((iocb->ki_flags & (IOCB_NOWAIT | IOCB_DIRECT)) == IOCB_NOWAIT)
>>> return -EOPNOTSUPP;
>>>
>>> - iov_iter_truncate(from, size - iocb->ki_pos);
>>> + size -= iocb->ki_pos;
>>> + if (iov_iter_count(from) > size) {
>>> + shorted = iov_iter_count(from) - size;
>>> + iov_iter_truncate(from, size);
>>> + }
>>>
>>> blk_start_plug(&plug);
>>> ret = __generic_file_write_iter(iocb, from);
>>> if (ret > 0)
>>> ret = generic_write_sync(iocb, ret);
>>> + iov_iter_reexpand(from, iov_iter_count(from) + shorted);
>>> blk_finish_plug(&plug);
>>> return ret;
>>> }
>>> @@ -1714,13 +1720,21 @@ ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
>>> struct inode *bd_inode = bdev_file_inode(file);
>>> loff_t size = i_size_read(bd_inode);
>>> loff_t pos = iocb->ki_pos;
>>> + size_t shorted = 0;
>>> + ssize_t ret;
>>>
>>> if (pos >= size)
>>> return 0;
>>>
>>> size -= pos;
>>> - iov_iter_truncate(to, size);
>>> - return generic_file_read_iter(iocb, to);
>>> + if (iov_iter_count(to) > size) {
>>> + shorted = iov_iter_count(to) - size;
>>> + iov_iter_truncate(to, size);
>>> + }
>>> +
>>> + ret = generic_file_read_iter(iocb, to);
>>> + iov_iter_reexpand(to, iov_iter_count(to) + shorted);
>>> + return ret;
>>> }
>>> EXPORT_SYMBOL_GPL(blkdev_read_iter);
>>>
>>>
>>
>
--
Pavel Begunkov
