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Sun, 30 Nov 2025 04:04:50 -0800 (PST) From: Prithvi Tambewagh To: socketcan@hartkopp.net Cc: Prithvi Tambewagh , linux-can@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: Feedback provided on question about KMSAN: uninit-value in can_receive Date: Sun, 30 Nov 2025 17:34:42 +0530 Message-Id: <20251130120442.289280-1-activprithvi@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <0c98b1c4-3975-4bf5-9049-9d7f10d22a6d@hartkopp.net> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hello Oliver, Thanks for the feedback! I now understand how struct can_skb_priv is reserved in the headroom, more clearly, given that I am relatively new to kernel development. I agree on your patch. I tested it locally using the reproducer program for this bug provided by syzbot and it didn't crash the kernel. Also, I checked the patch here https://lore.kernel.org/linux-can/20191207183418.28868-1-socketcan@hartkopp.net/ looking at it, I think your patch will work fine with the above patch as well, since data will be accessed at skb->data - sizeof(struct can_skb_priv) which is the intended place for it, according to te action of can_skb_reserve() which increases headroom by length sizeof(struct can_skb_priv), reserving the space just before skb->data. I think it solves this specific KMSAN bug. Kindly correct me if I am wrong. Would you like to fix this bug by sending your patch upstream? Or else shall I send this patch upstream and mention your name in Suggested-by tag? Thank you, Prithvi Tambewagh