Re: [PATCH v4] qcow2-bitmap: Fix uint64_t left-shift overflow

[Vladimir Sementsov-Ogievskiy]

01.11.2019 12:34, Tuguoyi wrote:
> On 01.11.2019 17:25 Vladimir Sementsov-Ogievskiy wrote:
>> 01.11.2019 10:37, Tuguoyi wrote:
>>> There are two issues in In check_constraints_on_bitmap(),
>>> 1) The sanity check on the granularity will cause uint64_t integer
>>> left-shift overflow when cluster_size is 2M and the granularity is
>>> BIGGER than 32K.
>>> 2) The way to calculate image size that the maximum bitmap supported
>>> can map to is a bit incorrect.
>>> This patch fix it by add a helper function to calculate the number of
>>> bytes needed by a normal bitmap in image and compare it to the maximum
>>> bitmap bytes supported by qemu.
>>>
>>> Fixes: 5f72826e7fc62167cf3a
>>> Signed-off-by: Guoyi Tu <address@hidden>
>>
>> You forget my
>> Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> 
> Sorry for that, it's my first time to submit patch to qemu, and should I send 
> another patch or not ?

Good start!

No, you shouldn't. Maintainer will take such marks (and may be other proposed
improvements for commit message like this "Fixes: ", when applying, so no 
reason to resend.

Also, when sending a new version of patch, summarize what was changed since 
previous version
(you may do it under "---" which follows commit message, or in cover letter if 
it's
a patch set with several patches.

> 
>> (I don't see changes except add "Fixes: " to commit msg and put
>> get_bitmap_bytes_needed definition header into one line.)
> 
> Yes, Only minor changes are made, including removing 'inline' keyword.
> 
> Thanks for your patience in reviewing >
>>> ---
>>>    block/qcow2-bitmap.c | 14 +++++++++++---
>>>    1 file changed, 11 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c index
>>> 98294a7..ef9ef62 100644
>>> --- a/block/qcow2-bitmap.c
>>> +++ b/block/qcow2-bitmap.c
>>> @@ -142,6 +142,13 @@ static int check_table_entry(uint64_t entry, int
>> cluster_size)
>>>        return 0;
>>>    }
>>>
>>> +static int64_t get_bitmap_bytes_needed(int64_t len, uint32_t
>>> +granularity) {
>>> +    int64_t num_bits = DIV_ROUND_UP(len, granularity);
>>> +
>>> +    return DIV_ROUND_UP(num_bits, 8); }
>>> +
>>>    static int check_constraints_on_bitmap(BlockDriverState *bs,
>>>                                           const char *name,
>>>                                           uint32_t granularity, @@
>>> -150,6 +157,7 @@ static int check_constraints_on_bitmap(BlockDriverState
>> *bs,
>>>        BDRVQcow2State *s = bs->opaque;
>>>        int granularity_bits = ctz32(granularity);
>>>        int64_t len = bdrv_getlength(bs);
>>> +    int64_t bitmap_bytes;
>>>
>>>        assert(granularity > 0);
>>>        assert((granularity & (granularity - 1)) == 0); @@ -171,9 +179,9
>>> @@ static int check_constraints_on_bitmap(BlockDriverState *bs,
>>>            return -EINVAL;
>>>        }
>>>
>>> -    if ((len > (uint64_t)BME_MAX_PHYS_SIZE << granularity_bits) ||
>>> -        (len > (uint64_t)BME_MAX_TABLE_SIZE * s->cluster_size <<
>>> -               granularity_bits))
>>> +    bitmap_bytes = get_bitmap_bytes_needed(len, granularity);
>>> +    if ((bitmap_bytes > (uint64_t)BME_MAX_PHYS_SIZE) ||
>>> +        (bitmap_bytes > (uint64_t)BME_MAX_TABLE_SIZE *
>>> + s->cluster_size))
>>>        {
>>>            error_setg(errp, "Too much space will be occupied by the
>> bitmap. "
>>>                       "Use larger granularity");
>>>
>>
>>
>> --
>> Best regards,
>> Vladimir


-- 
Best regards,
Vladimir