From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Daniel Borkmann , Stephen Hemminger , Arnaldo Carvalho de Melo , "David S. Miller" , Kamal Mostafa Subject: [PATCH 3.8 164/166] net: llc: fix use after free in llc_ui_recvmsg Date: Wed, 15 Jan 2014 13:52:58 -0800 Message-Id: <1389822780-4729-165-git-send-email-kamal@canonical.com> In-Reply-To: <1389822780-4729-1-git-send-email-kamal@canonical.com> References: <1389822780-4729-1-git-send-email-kamal@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.8.13.16 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Daniel Borkmann [ Upstream commit 4d231b76eef6c4a6bd9c96769e191517765942cb ] While commit 30a584d944fb fixes datagram interface in LLC, a use after free bug has been introduced for SOCK_STREAM sockets that do not make use of MSG_PEEK. The flow is as follow ... if (!(flags & MSG_PEEK)) { ... sk_eat_skb(sk, skb, false); ... } ... if (used + offset < skb->len) continue; ... where sk_eat_skb() calls __kfree_skb(). Therefore, cache original length and work on skb_len to check partial reads. Fixes: 30a584d944fb ("[LLX]: SOCK_DGRAM interface fixes") Signed-off-by: Daniel Borkmann Cc: Stephen Hemminger Cc: Arnaldo Carvalho de Melo Signed-off-by: David S. Miller Signed-off-by: Kamal Mostafa --- net/llc/af_llc.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c index 8870988..c3ee805 100644 --- a/net/llc/af_llc.c +++ b/net/llc/af_llc.c @@ -715,7 +715,7 @@ static int llc_ui_recvmsg(struct kiocb *iocb, struct socket *sock, unsigned long cpu_flags; size_t copied = 0; u32 peek_seq = 0; - u32 *seq; + u32 *seq, skb_len; unsigned long used; int target; /* Read at least this many bytes */ long timeo; @@ -812,6 +812,7 @@ static int llc_ui_recvmsg(struct kiocb *iocb, struct socket *sock, } continue; found_ok_skb: + skb_len = skb->len; /* Ok so how much can we use? */ used = skb->len - offset; if (len < used) @@ -844,7 +845,7 @@ static int llc_ui_recvmsg(struct kiocb *iocb, struct socket *sock, } /* Partial read */ - if (used + offset < skb->len) + if (used + offset < skb_len) continue; } while (len > 0); -- 1.8.3.2