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Date: Thu, 4 Feb 2016 09:38:58 +0800
From: Fam Zheng <famz@redhat.com>
Message-ID: <20160204013858.GA5187@ad.usersys.redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] qemu-img: initialize MapEntry object
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To: John Snow <jsnow@redhat.com>
Cc: kwolf@redhat.com, qemu-devel@nongnu.org, qemu-block@nongnu.org

On Wed, 02/03 18:38, John Snow wrote:
> Commit 16b0d555 introduced an issue where we are not initializing
> has_filename for the 'next' MapEntry object, which leads to interesting
> errors in Valgrind and Clang -fsanitize=undefined both.
> 
> Zero the stack object at allocation AND make sure the utility to
> populate the fields properly marks has_filename as false if applicable.
> 
> Signed-off-by: John Snow <jsnow@redhat.com>
> ---
>  qemu-img.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/qemu-img.c b/qemu-img.c
> index f121980..5a85178 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -2231,6 +2231,9 @@ static int get_block_status(BlockDriverState *bs, int64_t sector_num,
>      if (file && e->has_offset) {
>          e->has_filename = true;
>          e->filename = file->filename;
> +    } else {
> +        e->has_filename = false;
> +        e->filename = NULL;
>      }
>      return 0;
>  }
> @@ -2264,7 +2267,7 @@ static int img_map(int argc, char **argv)
>      BlockDriverState *bs;
>      const char *filename, *fmt, *output;
>      int64_t length;
> -    MapEntry curr = { .length = 0 }, next;
> +    MapEntry curr = { .length = 0 }, next = { .length = 0 };
>      int ret = 0;
>  
>      fmt = NULL;
> -- 
> 2.4.3
> 

Reviewed-by: Fam Zheng <famz@redhat.com>