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Re: [Qemu-block] [PATCH for 2.10 08/35] qcow2: fix null pointer derefere


From: Eric Blake
Subject: Re: [Qemu-block] [PATCH for 2.10 08/35] qcow2: fix null pointer dereference
Date: Mon, 24 Jul 2017 13:52:23 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1

On 07/24/2017 01:27 PM, Philippe Mathieu-Daudé wrote:
> It seems this assert() was somehow misplaced.
> 
> block/qcow2-refcount.c:2193:42: warning: Array access (from variable 
> 'on_disk_reftable') results in a null pointer dereference
>         on_disk_reftable[refblock_index] = refblock_offset;
>         ~~~~~~~~~~~~~~~~                 ^
> 
> Reported-by: Clang Static Analyzer
> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> ---
>  block/qcow2-refcount.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Eric Blake <address@hidden>

> 
> diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
> index c9b0dcb4f3..168fc32e7b 100644
> --- a/block/qcow2-refcount.c
> +++ b/block/qcow2-refcount.c
> @@ -2189,6 +2189,8 @@ write_refblocks:
>               * this will leak that range, but we can easily fix that by 
> running
>               * a leak-fixing check after this rebuild operation */
>              reftable_offset = -1;
> +        } else {
> +            assert(on_disk_reftable);
>          }
>          on_disk_reftable[refblock_index] = refblock_offset;
>  
> @@ -2258,8 +2260,6 @@ write_refblocks:
>          goto write_refblocks;
>      }
>  
> -    assert(on_disk_reftable);
> -
>      for (refblock_index = 0; refblock_index < reftable_size; 
> refblock_index++) {
>          cpu_to_be64s(&on_disk_reftable[refblock_index]);
>      }
> 

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

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