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([2405:201:31:d869:9fd4:f657:3c3c:9fd0]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-29b5b25c104sm191816515ad.54.2025.11.26.00.57.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Nov 2025 00:57:29 -0800 (PST) From: ssrane_b23@ee.vjti.ac.in X-Google-Original-From: ssranevjti@gmail.com To: Oliver Hartkopp , Marc Kleine-Budde , Jamal Hadi Salim , Cong Wang , Jiri Pirko , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: Simon Horman , Rostislav Lisovy , linux-can@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, linux-kernel-mentees@lists.linux.dev, david.hunter.linux@gmail.com, khalid@kernel.org, Shaurya Rane , syzbot+5d8269a1e099279152bc@syzkaller.appspotmail.com Subject: [PATCH v3] net/sched: em_canid: fix uninit-value in em_canid_match Date: Wed, 26 Nov 2025 14:27:18 +0530 Message-Id: <20251126085718.50808-1-ssranevjti@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel-mentees@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Shaurya Rane Use pskb_may_pull() to ensure a complete CAN frame is present in the linear data buffer before reading the CAN ID. A simple skb->len check is insufficient because it only verifies the total data length but does not guarantee the data is present in skb->data (it could be in fragments). pskb_may_pull() both validates the length and pulls fragmented data into the linear buffer if necessary, making it safe to directly access skb->data. Reported-by: syzbot+5d8269a1e099279152bc@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=5d8269a1e099279152bc Fixes: f057bbb6f9ed ("net: em_canid: Ematch rule to match CAN frames according to their identifiers") Signed-off-by: Shaurya Rane --- v3: Use CAN_MTU to validate a complete CAN frame is present v2: Use pskb_may_pull() instead of skb->len check to properly handle fragmented skbs --- net/sched/em_canid.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/sched/em_canid.c b/net/sched/em_canid.c index 5337bc462755..2d27f91d8441 100644 --- a/net/sched/em_canid.c +++ b/net/sched/em_canid.c @@ -99,6 +99,9 @@ static int em_canid_match(struct sk_buff *skb, struct tcf_ematch *m, int i; const struct can_filter *lp; + if (!pskb_may_pull(skb, CAN_MTU)) + return 0; + can_id = em_canid_get_id(skb); if (can_id & CAN_EFF_FLAG) { -- 2.34.1