From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=53896 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Q1mkZ-0001wF-P2 for qemu-devel@nongnu.org; Mon, 21 Mar 2011 17:34:56 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Q1mkY-0000bG-Aw for qemu-devel@nongnu.org; Mon, 21 Mar 2011 17:34:55 -0400 Received: from e32.co.us.ibm.com ([32.97.110.150]:41970) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Q1mkY-0000aH-5W for qemu-devel@nongnu.org; Mon, 21 Mar 2011 17:34:54 -0400 Received: from d03relay01.boulder.ibm.com (d03relay01.boulder.ibm.com [9.17.195.226]) by e32.co.us.ibm.com (8.14.4/8.13.1) with ESMTP id p2LLO24x011451 for ; Mon, 21 Mar 2011 15:24:02 -0600 Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by d03relay01.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p2LLYj8N092232 for ; Mon, 21 Mar 2011 15:34:45 -0600 Received: from d03av02.boulder.ibm.com (loopback [127.0.0.1]) by d03av02.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p2LLYiwY019188 for ; Mon, 21 Mar 2011 15:34:45 -0600 Message-ID: <4D87C471.2000004@linux.vnet.ibm.com> Date: Mon, 21 Mar 2011 14:34:41 -0700 From: "Venkateswararao Jujjuri (JV)" MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH] v9fs_walk: As per 9p2000 RFC, MAXWELEM >= nwnames >= 0. References: <1300732315-1997-1-git-send-email-harsh@linux.vnet.ibm.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: Harsh Prateek Bora , qemu-devel@nongnu.org, aneesh.kumar@linux.vnet.ibm.com On 3/21/2011 2:16 PM, Stefan Hajnoczi wrote: > On Mon, Mar 21, 2011 at 6:31 PM, Harsh Prateek Bora > wrote: >> The nwnames field in TWALK message is assumed to be >=0 and <= MAXWELEM >> which is defined as macro P9_MAXWELEM (16) in virtio-9p.h as per 9p2000 RFC. >> Appropriate changes are required in V9fsWalkState and v9fs_walk. >> >> Signed-off-by: Harsh Prateek Bora >> --- >> hw/9pfs/virtio-9p.c | 5 ++++- >> hw/9pfs/virtio-9p.h | 2 +- >> 2 files changed, 5 insertions(+), 2 deletions(-) >> >> diff --git a/hw/9pfs/virtio-9p.c b/hw/9pfs/virtio-9p.c >> index 9b44bd0..b782a19 100644 >> --- a/hw/9pfs/virtio-9p.c >> +++ b/hw/9pfs/virtio-9p.c >> @@ -1805,7 +1805,7 @@ static void v9fs_walk(V9fsState *s, V9fsPDU *pdu) >> vs->offset += pdu_unmarshal(vs->pdu, vs->offset, "ddw", &fid, >> &newfid, &vs->nwnames); >> >> - if (vs->nwnames) { >> + if (vs->nwnames <= P9_MAXWELEM) { >> vs->wnames = qemu_mallocz(sizeof(vs->wnames[0]) * vs->nwnames); >> >> vs->qids = qemu_mallocz(sizeof(vs->qids[0]) * vs->nwnames); >> @@ -1814,6 +1814,9 @@ static void v9fs_walk(V9fsState *s, V9fsPDU *pdu) >> vs->offset += pdu_unmarshal(vs->pdu, vs->offset, "s", >> &vs->wnames[i]); >> } >> + } else { >> + err = -EINVAL; vs->nwnames = 0; will take care of v9fs_walk_complete() issue Stefan brought up. >> + goto out; >> } > > v9fs_walk_complete() will attempt to free wnames, qids, and the wnames > strings. Freeing the strings will crash because we're indexing into > an array based off a NULL pointer. > > It would be very handy to have a PDU-level test suite. You could then > construct a PDU with an invalid nwnames field and exercise this code > path. Perhaps a debug ioctl in Linux v9fs that allows a userspace > tool to pass PDUs through will do? Ioctl way was ruled out in the past discussion. But yes we have in plan on to introduce a test suite of this kind. Malahal (who is on vacation) will start this work from early April. Thanks, JV > > Stefan