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Date: Mon, 4 Aug 2014 14:26:25 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
Message-ID: <20140804122625.GC15491@redhat.com>
References: <1407140744-11948-1-git-send-email-zhang.zhanghailiang@huawei.com>
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In-Reply-To: <1407140744-11948-5-git-send-email-zhang.zhanghailiang@huawei.com>
Subject: Re: [Qemu-devel] [PATCH 4/4] ivshmem: check the value returned by
	fstat()
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To: zhanghailiang <zhang.zhanghailiang@huawei.com>
Cc: kwolf@redhat.com, stefanha@redhat.com, luonengjun@huawei.com, qemu-devel@nongnu.org, lcapitulino@redhat.com, alex@alex.org.uk, pbonzini@redhat.com, peter.huangpeng@huawei.com

On Mon, Aug 04, 2014 at 04:25:44PM +0800, zhanghailiang wrote:
> The function fstat() may fail, so check its return value.
> 
> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
> ---
>  hw/misc/ivshmem.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
> index 768e528..2667e9f 100644
> --- a/hw/misc/ivshmem.c
> +++ b/hw/misc/ivshmem.c
> @@ -324,7 +324,10 @@ static int check_shm_size(IVShmemState *s, int fd) {
>  
>      struct stat buf;
>  
> -    fstat(fd, &buf);
> +    if (fstat(fd, &buf) < 0) {
> +        fprintf(stderr, "Cannot stat IVSHMEM: %s\n", strerror(errno));
> +        return -1;
> +    }
>

That's a confusing error message:
1. You don't stat ivshmem. You stat a shmem fd. Also best to print fd #.
2. Tell the user what action was taken, e.g. IVSHMEM failed to start.
  
>      if (s->ivshmem_size > buf.st_size) {
>          fprintf(stderr,
> -- 
> 1.7.12.4
>