Re: [Qemu-devel] [PATCH for-2.11] qcow2: Fix overly broad madvise()

[Eric Blake <eblake@redhat.com>]

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On 11/14/2017 12:41 PM, Max Reitz wrote:
> @mem_size and @offset are both size_t, thus subtracting them from one
> another will just return a big size_t if mem_size < offset -- even more
> obvious here because the result is stored in another size_t.
> 
> Checking that result to be positive is therefore not sufficient to
> excluse the case that offset > mem_size.  Thus, we currently sometimes

s/excluse/exclude/

> issue an madvise() over a very large address range.
> 
> This is triggered by iotest 163, but with -m64, this does not result in
> tangible problems.  But with -m32, this test produces three segfaults,
> all of which are fixed by this patch.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  block/qcow2-cache.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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