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From: Juan Quintela <quintela@redhat.com>
In-Reply-To: <20180509111258.GE2527@work-vm> (David Alan Gilbert's message of
	"Wed, 9 May 2018 12:12:59 +0100")
References: <20180425112723.1111-1-quintela@redhat.com>
	<20180425112723.1111-12-quintela@redhat.com>
	<20180502180447.GM2679@work-vm> <87bmdp5bmv.fsf@secure.laptop>
	<20180509111258.GE2527@work-vm>
Reply-To: quintela@redhat.com
Date: Wed, 09 May 2018 21:46:04 +0200
Message-ID: <87h8ng394z.fsf@secure.laptop>
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Subject: Re: [Qemu-devel] [PATCH v12 11/21] migration: Create multifd packet
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To: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: qemu-devel@nongnu.org, lvivier@redhat.com, peterx@redhat.com

"Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> * Juan Quintela (quintela@redhat.com) wrote:
>> "Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
>> > * Juan Quintela (quintela@redhat.com) wrote:
>> > I think that needs validating to ensure that the source didn't
>> > send us junk and cause us to overwrite after the end of block->host
>> 
>>         if (offset > block->used_length) {
>>             error_setg(errp, "multifd: offest too long %" PRId64
>>                        " (max %" PRId64 ")",
>>                        offset, block->max_length);
>>             return -1;
>>         }
>> ??
>
> It's probably  (offset + TARGET_PAGE_SIZE) that needs checking
> but it needs doing in a wrap-safe way.
>

        if ((offset + TARGET_PAGE_SIZE) < offset) {
            error_setg(errp, "multifd: offset %" PRId64 " wraps around"
                       " with offset: %" PRId64, offset, block->max_length);
            return -1;
        }
        if ((offset + TARGET_PAGE_SIZE) > block->used_length) {
            error_setg(errp, "multifd: offset too long %" PRId64
                       " (max %" PRId64 ")",
                       offset, block->max_length);
            return -1;
        }

Sometimes I wonder how is that we don't have

ramblock_contains_range(ramblock, start, size);

But well, c'est la vie.

Later, Juan.