netdev - [PATCHv2 net] sctp: use the correct skb for security_sctp_assoc

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Date:   Thu,  7 Apr 2022 09:24:22 -0400
From:   Xin Long <lucien.xin@...il.com>
To:     network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org
Cc:     davem@...emloft.net, kuba@...nel.org,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Neil Horman <nhorman@...driver.com>, omosnace@...hat.com
Subject: [PATCHv2 net] sctp: use the correct skb for security_sctp_assoc_request

Yi Chen reported an unexpected sctp connection abort, and it occurred when
COOKIE_ECHO is bundled with DATA Fragment by SCTP HW GSO. As the IP header
is included in chunk->head_skb instead of chunk->skb, it failed to check
IP header version in security_sctp_assoc_request().

According to Ondrej, SELinux only looks at IP header (address and IPsec
options) and XFRM state data, and these are all included in head_skb for
SCTP HW GSO packets. So fix it by using head_skb when calling
security_sctp_assoc_request() in processing COOKIE_ECHO.

v1->v2:
  - As Ondrej noticed, chunk->head_skb should also be used for
    security_sctp_assoc_established() in sctp_sf_do_5_1E_ca().

Fixes: e215dab1c490 ("security: call security_sctp_assoc_request in sctp_sf_do_5_1D_ce")
Reported-by: Yi Chen <yiche@...hat.com>
Signed-off-by: Xin Long <lucien.xin@...il.com>
---
 net/sctp/sm_statefuns.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index 7f342bc12735..52edee1322fc 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -781,7 +781,7 @@ enum sctp_disposition sctp_sf_do_5_1D_ce(struct net *net,
 		}
 	}
 
-	if (security_sctp_assoc_request(new_asoc, chunk->skb)) {
+	if (security_sctp_assoc_request(new_asoc, chunk->head_skb ?: chunk->skb)) {
 		sctp_association_free(new_asoc);
 		return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
 	}
@@ -932,7 +932,7 @@ enum sctp_disposition sctp_sf_do_5_1E_ca(struct net *net,
 
 	/* Set peer label for connection. */
 	if (security_sctp_assoc_established((struct sctp_association *)asoc,
-					    chunk->skb))
+					    chunk->head_skb ?: chunk->skb))
 		return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
 
 	/* Verify that the chunk length for the COOKIE-ACK is OK.
@@ -2262,7 +2262,7 @@ enum sctp_disposition sctp_sf_do_5_2_4_dupcook(
 	}
 
 	/* Update socket peer label if first association. */
-	if (security_sctp_assoc_request(new_asoc, chunk->skb)) {
+	if (security_sctp_assoc_request(new_asoc, chunk->head_skb ?: chunk->skb)) {
 		sctp_association_free(new_asoc);
 		return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
 	}
-- 
2.31.1