From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Elder Subject: Re: [PATCH 2/3] libceph: fix overflow in osdmap_decode() Date: Wed, 06 Jun 2012 11:26:12 -0500 Message-ID: <4FCF84A4.4040005@dreamhost.com> References: <1335682765-1643-1-git-send-email-xi.wang@gmail.com> <1335682765-1643-2-git-send-email-xi.wang@gmail.com> Reply-To: elder@inktank.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from mail.hq.newdream.net ([66.33.206.127]:36321 "EHLO mail.hq.newdream.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756643Ab2FFQ0H (ORCPT ); Wed, 6 Jun 2012 12:26:07 -0400 In-Reply-To: <1335682765-1643-2-git-send-email-xi.wang@gmail.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Xi Wang Cc: Sage Weil , ceph-devel@vger.kernel.org On 04/29/2012 01:59 AM, Xi Wang wrote: > On 32-bit systems, a large `n' would overflow `n * sizeof(u32)' and bypass > the check ceph_decode_need(p, end, n * sizeof(u32), bad). It would also > overflow the subsequent kmalloc() size, leading to out-of-bounds write. This looks good. Your previous patch made me look at something else though. If you can think of a good solution would you be willing to send a patch to implement it? (See below.) I won't hold up committing this for it, but I'd like your opinion. Reviewed-by: Alex Elder > Signed-off-by: Xi Wang > --- > net/ceph/osdmap.c | 3 +++ > 1 files changed, 3 insertions(+), 0 deletions(-) > > diff --git a/net/ceph/osdmap.c b/net/ceph/osdmap.c > index f80afc3..774eac6 100644 > --- a/net/ceph/osdmap.c > +++ b/net/ceph/osdmap.c > @@ -670,6 +670,9 @@ struct ceph_osdmap *osdmap_decode(void **p, void *end) Just above here we see: /* pg_temp */ ceph_decode_32_safe(p, end, len, bad); for (i = 0; i < len; i++) { We haven't validated "len" here either. Looking at it I'm not sure we can do much, but I think we do know a few things should be true: - (len & (sizeof (u32) - 1)) == 0 - len <= (UINT_MAX / (sizeof (struct ceph_pg) + sizeof (u32))) and further, if it's invalid to have a value for pg->len of zero, then we can instead assert: - len <= (UINT_MAX / (sizeof (struct ceph_pg) + 2 * sizeof (u32))) I don't know if it's that important do do a check like this though. I appreciate these detail-oriented fixes that you've been sending. > ceph_decode_need(p, end, sizeof(u32) + sizeof(u64), bad); > ceph_decode_copy(p, &pgid, sizeof(pgid)); > n = ceph_decode_32(p); > + err = -EINVAL; > + if (n > (UINT_MAX - sizeof(*pg)) / sizeof(u32)) > + goto bad; > ceph_decode_need(p, end, n * sizeof(u32), bad); > err = -ENOMEM; > pg = kmalloc(sizeof(*pg) + n*sizeof(u32), GFP_NOFS);