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Date: Thu, 14 Aug 2014 12:36:22 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
Message-ID: <20140814103622.GI31346@redhat.com>
References: <1408001361-13580-1-git-send-email-zhang.zhanghailiang@huawei.com>
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In-Reply-To: <1408001361-13580-11-git-send-email-zhang.zhanghailiang@huawei.com>
Subject: Re: [Qemu-devel] [PATCH v6 10/10] block/vvfat: fix setbuf stream
 parameter may be NULL
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To: zhanghailiang <zhang.zhanghailiang@huawei.com>
Cc: kwolf@redhat.com, lkurusa@redhat.com, qemu-trivial@nongnu.org, jan.kiszka@siemens.com, riku.voipio@iki.fi, mjt@tls.msk.ru, qemu-devel@nongnu.org, lcapitulino@redhat.com, stefanha@redhat.com, Li Liu <john.liuli@huawei.com>, luonengjun@huawei.com, pbonzini@redhat.com, peter.huangpeng@huawei.com, alex.bennee@linaro.org, rth@twiddle.net

On Thu, Aug 14, 2014 at 03:29:21PM +0800, zhanghailiang wrote:
> From: Li Liu <john.liuli@huawei.com>
> 
> fopen() may return NULL which will cause setbuf() segmentfault
> 
> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
> Signed-off-by: Li Liu <john.liuli@huawei.com>
> ---
>  block/vvfat.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/block/vvfat.c b/block/vvfat.c
> index 70176b1..6889ea9 100644
> --- a/block/vvfat.c
> +++ b/block/vvfat.c
> @@ -1084,7 +1084,10 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
>  
>  DLOG(if (stderr == NULL) {
>      stderr = fopen("vvfat.log", "a");
> -    setbuf(stderr, NULL);
> +
> +    if (stderr) {
> +        setbuf(stderr, NULL);
> +    }
>  })
>  
>      opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);

I would say assert on failure here.
If one is trying to debug, seeing no output will just confuse
matters more.

> -- 
> 1.7.12.4
>