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Sun, 26 Oct 2025 09:33:22 -0700 (PDT) Received: from [127.0.1.1] ([2406:7400:10c:a59a:a7b7:a351:9b3b:d26d]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-b71268bde68sm4837369a12.1.2025.10.26.09.33.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 26 Oct 2025 09:33:22 -0700 (PDT) From: Ranganath V N Date: Sun, 26 Oct 2025 22:03:12 +0530 Subject: [PATCH v3] net: sctp: fix KMSAN uninit-value in sctp_inq_pop Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251026-kmsan_fix-v3-1-2634a409fa5f@gmail.com> X-B4-Tracking: v=1; b=H4sIAEdN/mgC/22Myw6CMBQFf4XctTV9iG1Z+R/GGPoAbrRgWtNoC P9uYcXC5ZycmRmSj+gTNNUM0WdMOI0FxKECO7Rj7wm6wsAprxnlgjxCasd7hx8ilau5NFqfqYH yf0Vf5q11vRUeML2n+N3Sma3rv0pmhBFHlWXKGaWkvPShxefRTgHWSuZ787Q3+WpaoYXtjKaS7 c1lWX7X3VYF3AAAAA== To: Marcelo Ricardo Leitner , Xin Long , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman Cc: linux-sctp@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, syzbot+d101e12bccd4095460e7@syzkaller.appspotmail.com, Ranganath V N X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1761496398; l=1958; i=vnranganath.20@gmail.com; s=20250816; h=from:subject:message-id; bh=dkfgSRg3n/ubnVVhdVKVipSAGyUHeSxeTZAvC8QYEGI=; b=cXfC2grfwFoLTzuKTmqRsq4RmFBhH81YwCEK+w6/9OREBTgr7kj10VBf6eGGDduYtb9w//Hn/ uGQe23ZPQprDUJ2/t63/UnLKYIyUrrrQIs7T0xElPUnR1QpQ8ABqBaS X-Developer-Key: i=vnranganath.20@gmail.com; a=ed25519; pk=7mxHFYWOcIJ5Ls8etzgLkcB0M8/hxmOh8pH6Mce5Z1A= Fix an issue detected by syzbot: KMSAN reported an uninitialized-value access in sctp_inq_pop BUG: KMSAN: uninit-value in sctp_inq_pop The issue is actually caused by skb trimming via sk_filter() in sctp_rcv(). In the reproducer, skb->len becomes 1 after sk_filter(), which bypassed the original check: if (skb->len < sizeof(struct sctphdr) + sizeof(struct sctp_chunkhdr= ) + skb_transport_offset(skb)) To handle this safely, a new check should be performed after sk_filter(). Reported-by: syzbot+d101e12bccd4095460e7@syzkaller.appspotmail.com Tested-by: syzbot+d101e12bccd4095460e7@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3Dd101e12bccd4095460e7 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Suggested-by: Xin Long Signed-off-by: Ranganath V N Reviewed-by: Simon Horman --- KMSAN reported an uninitialized-value access in sctp_inq_pop --- Changes in v3: - fixes the patch format like fixes and closes tags. - Link to v2: https://lore.kernel.org/r/20251024-kmsan_fix-v2-1-dc393cfb907= 1@gmail.com Changes in v2: - changes in commit message as per the code changes. - fixed as per the suggestion. - Link to v1: https://lore.kernel.org/r/20251023-kmsan_fix-v1-1-d08c18db887= 7@gmail.com --- net/sctp/input.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/sctp/input.c b/net/sctp/input.c index 7e99894778d4..e119e460ccde 100644 --- a/net/sctp/input.c +++ b/net/sctp/input.c @@ -190,7 +190,7 @@ int sctp_rcv(struct sk_buff *skb) goto discard_release; nf_reset_ct(skb); =20 - if (sk_filter(sk, skb)) + if (sk_filter(sk, skb) || skb->len < sizeof(struct sctp_chunkhdr)) goto discard_release; =20 /* Create an SCTP packet structure. */ --- base-commit: 43e9ad0c55a369ecc84a4788d06a8a6bfa634f1c change-id: 20251023-kmsan_fix-78d527b9960b Best regards, --=20 Ranganath V N