From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48954) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XEbYn-0001Pu-Q3 for qemu-devel@nongnu.org; Tue, 05 Aug 2014 06:01:42 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XEbYh-00024C-O8 for qemu-devel@nongnu.org; Tue, 05 Aug 2014 06:01:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38003) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XEbYh-000244-GA for qemu-devel@nongnu.org; Tue, 05 Aug 2014 06:01:31 -0400 Date: Tue, 5 Aug 2014 12:00:24 +0200 From: "Michael S. Tsirkin" Message-ID: <20140805100024.GC24619@redhat.com> 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> <53E03AC9.2070806@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53E03AC9.2070806@huawei.com> 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: zhanghailiang 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 Tue, Aug 05, 2014 at 10:00:41AM +0800, zhanghailiang wrote: > 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. So put "exiting" In the error message then. > >>1.7.12.4 > >> > > > >. > > > > Best regards, > zhanghailiang