linux-kernel - [PATCH 4.4 06/15] net: avoid skb_warn_bad

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20170811220219.708246658@linuxfoundation.org>
Date:   Fri, 11 Aug 2017 15:02:20 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Willem de Bruijn <willemb@...gle.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.4 06/15] net: avoid skb_warn_bad_offload false positives on UFO

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Willem de Bruijn <willemb@...gle.com>

[ Upstream commit 8d63bee643f1fb53e472f0e135cae4eb99d62d19 ]

skb_warn_bad_offload triggers a warning when an skb enters the GSO
stack at __skb_gso_segment that does not have CHECKSUM_PARTIAL
checksum offload set.

Commit b2504a5dbef3 ("net: reduce skb_warn_bad_offload() noise")
observed that SKB_GSO_DODGY producers can trigger the check and
that passing those packets through the GSO handlers will fix it
up. But, the software UFO handler will set ip_summed to
CHECKSUM_NONE.

When __skb_gso_segment is called from the receive path, this
triggers the warning again.

Make UFO set CHECKSUM_UNNECESSARY instead of CHECKSUM_NONE. On
Tx these two are equivalent. On Rx, this better matches the
skb state (checksum computed), as CHECKSUM_NONE here means no
checksum computed.

See also this thread for context:
http://patchwork.ozlabs.org/patch/799015/

Fixes: b2504a5dbef3 ("net: reduce skb_warn_bad_offload() noise")
Signed-off-by: Willem de Bruijn <willemb@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/core/dev.c         |    2 +-
 net/ipv4/udp_offload.c |    2 +-
 net/ipv6/udp_offload.c |    2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2551,7 +2551,7 @@ static inline bool skb_needs_check(struc
 {
 	if (tx_path)
 		return skb->ip_summed != CHECKSUM_PARTIAL &&
-		       skb->ip_summed != CHECKSUM_NONE;
+		       skb->ip_summed != CHECKSUM_UNNECESSARY;

 	return skb->ip_summed == CHECKSUM_NONE;
 }
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -231,7 +231,7 @@ static struct sk_buff *udp4_ufo_fragment
 	if (uh->check == 0)
 		uh->check = CSUM_MANGLED_0;

-	skb->ip_summed = CHECKSUM_NONE;
+	skb->ip_summed = CHECKSUM_UNNECESSARY;

 	/* Fragment the skb. IP headers of the fragments are updated in
 	 * inet_gso_segment()
--- a/net/ipv6/udp_offload.c
+++ b/net/ipv6/udp_offload.c
@@ -86,7 +86,7 @@ static struct sk_buff *udp6_ufo_fragment
 		if (uh->check == 0)
 			uh->check = CSUM_MANGLED_0;

-		skb->ip_summed = CHECKSUM_NONE;
+		skb->ip_summed = CHECKSUM_UNNECESSARY;

 		/* Check if there is enough headroom to insert fragment header. */
 		tnl_hlen = skb_tnl_header_len(skb);