From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759248AbbIVR5Q (ORCPT ); Tue, 22 Sep 2015 13:57:16 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:43084 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759395AbbIVRyP (ORCPT ); Tue, 22 Sep 2015 13:54:15 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Herbert Xu , "David S. Miller" , Kamal Mostafa Subject: [PATCH 3.19.y-ckt 098/102] net: Fix skb csum races when peeking Date: Tue, 22 Sep 2015 10:52:34 -0700 Message-Id: <1442944358-1248-99-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1442944358-1248-1-git-send-email-kamal@canonical.com> References: <1442944358-1248-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.19 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.19.8-ckt7 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Herbert Xu [ Upstream commit 89c22d8c3b278212eef6a8cc66b570bc840a6f5a ] When we calculate the checksum on the recv path, we store the result in the skb as an optimisation in case we need the checksum again down the line. This is in fact bogus for the MSG_PEEK case as this is done without any locking. So multiple threads can peek and then store the result to the same skb, potentially resulting in bogus skb states. This patch fixes this by only storing the result if the skb is not shared. This preserves the optimisations for the few cases where it can be done safely due to locking or other reasons, e.g., SIOCINQ. Signed-off-by: Herbert Xu Acked-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Kamal Mostafa --- net/core/datagram.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/net/core/datagram.c b/net/core/datagram.c index f5cce20..e0a31cc 100644 --- a/net/core/datagram.c +++ b/net/core/datagram.c @@ -658,7 +658,8 @@ __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len) !skb->csum_complete_sw) netdev_rx_csum_fault(skb->dev); } - skb->csum_valid = !sum; + if (!skb_shared(skb)) + skb->csum_valid = !sum; return sum; } EXPORT_SYMBOL(__skb_checksum_complete_head); @@ -678,11 +679,13 @@ __sum16 __skb_checksum_complete(struct sk_buff *skb) netdev_rx_csum_fault(skb->dev); } - /* Save full packet checksum */ - skb->csum = csum; - skb->ip_summed = CHECKSUM_COMPLETE; - skb->csum_complete_sw = 1; - skb->csum_valid = !sum; + if (!skb_shared(skb)) { + /* Save full packet checksum */ + skb->csum = csum; + skb->ip_summed = CHECKSUM_COMPLETE; + skb->csum_complete_sw = 1; + skb->csum_valid = !sum; + } return sum; } -- 1.9.1