From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41925) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XEYaq-00026P-27 for qemu-devel@nongnu.org; Tue, 05 Aug 2014 02:51:37 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XEYah-0003Ng-QK for qemu-devel@nongnu.org; Tue, 05 Aug 2014 02:51:32 -0400 Received: from mx3-phx2.redhat.com ([209.132.183.24]:33057) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XEYah-0003NG-IM for qemu-devel@nongnu.org; Tue, 05 Aug 2014 02:51:23 -0400 Date: Tue, 5 Aug 2014 02:50:56 -0400 (EDT) From: Levente Kurusa Message-ID: <499586037.10574482.1407221456854.JavaMail.zimbra@redhat.com> In-Reply-To: <53E03AC9.2070806@huawei.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=utf-8 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: zhanghailiang Cc: kwolf@redhat.com, alex@alex.org.uk, "Michael S. Tsirkin" , luonengjun@huawei.com, qemu-devel@nongnu.org, lcapitulino@redhat.com, stefanha@redhat.com, pbonzini@redhat.com, peter huangpeng ----- Original Message ----- > 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. Yes, please return -1. All the errors fstat(2) can return in this scenario will be fatal to ivshmem. Exiting is probably not the best way to go, but I'm working on a fix for that at the moment, and for now, let's just exit, like all the other error paths do. Thanks, Levente Kurusa