[GEDI] [PATCH v3 05/17] block/io: support int64_t bytes in bdrv_co_do_pwrite_zeroes()
vsementsov at virtuozzo.com
Tue Jun 23 10:20:11 UTC 2020
11.05.2020 21:34, Eric Blake wrote:
> On 5/11/20 12:17 PM, Alberto Garcia wrote:
>> On Thu 30 Apr 2020 01:10:21 PM CEST, Vladimir Sementsov-Ogievskiy wrote:
>>> compute 'int tail' via % 'int alignment' - safe
>> tail = (offset + bytes) % alignment;
>> both are int64_t, no chance of overflow here?
> Good question - I know several places check that offset+bytes does not overflow, but did not specifically audit if this one does. Adding an assert() in this function may be easier than trying to prove all callers pass in safe values.
Hm, it's preexisting, as int64_t + int may overflow as well. Strange, but I don't see overflow check neither in blk_check_byte_request nor in bdrv_check_byte_request. Only discard, which recently dropped call of bdrv_check_byte_request() has this check.
I can add a patch for overflow check in blk_check_byte_request and bdrv_check_byte_request.. But what about alignment? There may be requests, for which bytes + offset doesn't overflow, but do overflow after aligning up. Refactor bdrv_pad_request() to return an error if we can't pad request due to overflow?
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