From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53653) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XEU67-0003Fz-TV for qemu-devel@nongnu.org; Mon, 04 Aug 2014 22:03:36 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XEU63-0000vK-2g for qemu-devel@nongnu.org; Mon, 04 Aug 2014 22:03:31 -0400 Received: from szxga03-in.huawei.com ([119.145.14.66]:4656) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XEU62-0000v3-F5 for qemu-devel@nongnu.org; Mon, 04 Aug 2014 22:03:26 -0400 Message-ID: <53E03AC9.2070806@huawei.com> Date: Tue, 5 Aug 2014 10:00:41 +0800 From: zhanghailiang MIME-Version: 1.0 References: <1407140744-11948-1-git-send-email-zhang.zhanghailiang@huawei.com> <1407140744-11948-5-git-send-email-zhang.zhanghailiang@huawei.com> <20140804122625.GC15491@redhat.com> In-Reply-To: <20140804122625.GC15491@redhat.com> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 4/4] ivshmem: check the value returned by fstat() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" 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 Hi Michael, Thanks for your review of this patch! > 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 >> --- >> 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 #. I will add this in next version of the patch. > 2. Tell the user what action was taken, e.g. IVSHMEM failed to start. > >> if (s->ivshmem_size> buf.st_size) { >> fprintf(stderr, >> -- I have check the places of calling this function, And found that, if this function return -1, qemu will call exit(-1). One of the callers is ivshmem_read(), the purpose of check_shm_size() is to forbid guest to map more memory than the object has allocated. So here is it suitable to return -1 if fstat() failed? Or just give a warning message and return 0? what's your opinion? Thanks. >> 1.7.12.4 >> > > . > Best regards, zhanghailiang