Re: [Qemu-devel] [PATCH v5 2/3] block/io: bdrv_pdiscard: support int64_t bytes parameter

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

30.04.2019 12:24, Stefano Garzarella wrote:
> On Tue, Apr 23, 2019 at 03:57:05PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>> This fixes at least one overflow in qcow2_process_discards, which
>> passes 64bit region length to bdrv_pdiscard where bytes (or sectors in
>> the past) parameter is int since its introduction in 0b919fae.
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> ---
>>   include/block/block.h |  4 ++--
>>   block/io.c            | 16 ++++++++--------
>>   2 files changed, 10 insertions(+), 10 deletions(-)
>>
>> diff --git a/include/block/block.h b/include/block/block.h
>> index c7a26199aa..69fa18867e 100644
>> --- a/include/block/block.h
>> +++ b/include/block/block.h
>> @@ -432,8 +432,8 @@ void bdrv_drain_all(void);
>>       AIO_WAIT_WHILE(bdrv_get_aio_context(bs_),              \
>>                      cond); })
>>   
>> -int bdrv_pdiscard(BdrvChild *child, int64_t offset, int bytes);
>> -int bdrv_co_pdiscard(BdrvChild *child, int64_t offset, int bytes);
>> +int bdrv_pdiscard(BdrvChild *child, int64_t offset, int64_t bytes);
>> +int bdrv_co_pdiscard(BdrvChild *child, int64_t offset, int64_t bytes);
>>   int bdrv_has_zero_init_1(BlockDriverState *bs);
>>   int bdrv_has_zero_init(BlockDriverState *bs);
>>   bool bdrv_unallocated_blocks_are_zero(BlockDriverState *bs);
>> diff --git a/block/io.c b/block/io.c
>> index dfc153b8d8..16b6c5d855 100644
>> --- a/block/io.c
>> +++ b/block/io.c
>> @@ -2653,7 +2653,7 @@ int bdrv_flush(BlockDriverState *bs)
>>   typedef struct DiscardCo {
>>       BdrvChild *child;
>>       int64_t offset;
>> -    int bytes;
>> +    int64_t bytes;
>>       int ret;
>>   } DiscardCo;
>>   static void coroutine_fn bdrv_pdiscard_co_entry(void *opaque)
>> @@ -2664,14 +2664,15 @@ static void coroutine_fn bdrv_pdiscard_co_entry(void *opaque)
>>       aio_wait_kick();
>>   }
>>   
>> -int coroutine_fn bdrv_co_pdiscard(BdrvChild *child, int64_t offset, int bytes)
>> +int coroutine_fn bdrv_co_pdiscard(BdrvChild *child, int64_t offset,
>> +                                  int64_t bytes)
>>   {
>>       BdrvTrackedRequest req;
>>       int max_pdiscard, ret;
>>       int head, tail, align;
>>       BlockDriverState *bs = child->bs;
>>   
>> -    if (!bs || !bs->drv) {
>> +    if (!bs || !bs->drv || !bdrv_is_inserted(bs)) {
> 
> Should we describe this change in the commit message?

Honestly, don't want to resend the series for this.

> IIUC you added this check because you removed bdrv_check_byte_request()
> below,
> 
> Maybe we can also remove '!bs->drv', since it is checked in
> bdrv_is_inserted().

Hmm, on v4 Kevin commented, that bdrv_is_inserted not needed, and, as I understand, not only
in bdrv_co_pdiscard it should be removed, but it may be done later. So, I'd prefer to keep it
as is for now.

> 
>>           return -ENOMEDIUM;
>>       }
>>   
>> @@ -2679,9 +2680,8 @@ int coroutine_fn bdrv_co_pdiscard(BdrvChild *child, int64_t offset, int bytes)
>>           return -EPERM;
>>       }
>>   
>> -    ret = bdrv_check_byte_request(bs, offset, bytes);
>> -    if (ret < 0) {
>> -        return ret;
>> +    if (offset < 0 || bytes < 0 || bytes > INT64_MAX - offset) {
>> +        return -EIO;
>>       }
> 
> Should we check if 'bytes' is greater than
> 'BDRV_REQUEST_MAX_SECTORS << BDRV_SECTOR_BITS'?
> 

No, as we are contrariwise trying to support large bytes parameter in bdrv_co_pdiscard, which will
exceed max request. If @bytes is large, it will be divided into several smaller requests in the
following loop.


-- 
Best regards,
Vladimir