From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4FBA7238145; Mon, 27 Oct 2025 19:19:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761592774; cv=none; b=qysN2+gF4Aw745v0zvzihlgUoOUW9zUaq0xEuvHLhoL8Mqa8h+heGcRF+T2s3ew3vFXXBROYBdBBw0bokhxjkJExxsCtLq3ezj8rqFzYPN6xbabEmS2oaLapr/+RVXUOjkrW2aywZzMnPFi7qGAR7WyVGEHoOTFy4cSTvaIEayM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761592774; c=relaxed/simple; bh=2WQ/eHq0u6Q6/T0OWYzkWfWzA8l07ncEdXhad6S1sjk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fs9ebQQ72du+0l7+mw1P9ysEqYmOOGd+rNGQS3td74OhMFzjd46W5XB8sXi3NpgeCwA5do5uYGs6sbWkhhZC9GHGOGmJ+n01vw2TiHR0NqBtLF4IkSIGGtmyHJNP2gtLlhnUeP/CIPLidLVxa/CAYlMJtLYHDcTfMLmwO4WTstA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Su+U+Ed+; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Su+U+Ed+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D658AC4CEF1; Mon, 27 Oct 2025 19:19:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1761592774; bh=2WQ/eHq0u6Q6/T0OWYzkWfWzA8l07ncEdXhad6S1sjk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Su+U+Ed+te/9b7VJpLHOm1FzN3lGWINmqPbfGvG6WHYz0K9ZVrGK3UdA9THnGUf9Z a2+o6qq/w/V54p2Zsz1qXD/X79aBlBC90Mxx3gL6pLvMmZzE8ngO3DjkE29IRshli3 sK/9gEfoF7oPyczy71cd0pu+EcgbFPfOdO5cC1Ko= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+f6c3c066162d2c43a66c@syzkaller.appspotmail.com, Deepanshu Kartikey , Ian Abbott Subject: [PATCH 6.6 67/84] comedi: fix divide-by-zero in comedi_buf_munge() Date: Mon, 27 Oct 2025 19:36:56 +0100 Message-ID: <20251027183440.599500006@linuxfoundation.org> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20251027183438.817309828@linuxfoundation.org> References: <20251027183438.817309828@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Deepanshu Kartikey commit 87b318ba81dda2ee7b603f4f6c55e78ec3e95974 upstream. The comedi_buf_munge() function performs a modulo operation `async->munge_chan %= async->cmd.chanlist_len` without first checking if chanlist_len is zero. If a user program submits a command with chanlist_len set to zero, this causes a divide-by-zero error when the device processes data in the interrupt handler path. Add a check for zero chanlist_len at the beginning of the function, similar to the existing checks for !map and CMDF_RAWDATA flag. When chanlist_len is zero, update munge_count and return early, indicating the data was handled without munging. This prevents potential kernel panics from malformed user commands. Reported-by: syzbot+f6c3c066162d2c43a66c@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=f6c3c066162d2c43a66c Cc: stable@vger.kernel.org Signed-off-by: Deepanshu Kartikey Reviewed-by: Ian Abbott Link: https://patch.msgid.link/20250924102639.1256191-1-kartikey406@gmail.com Signed-off-by: Greg Kroah-Hartman --- drivers/comedi/comedi_buf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/comedi/comedi_buf.c +++ b/drivers/comedi/comedi_buf.c @@ -368,7 +368,7 @@ static unsigned int comedi_buf_munge(str unsigned int count = 0; const unsigned int num_sample_bytes = comedi_bytes_per_sample(s); - if (!s->munge || (async->cmd.flags & CMDF_RAWDATA)) { + if (!s->munge || (async->cmd.flags & CMDF_RAWDATA) || async->cmd.chanlist_len == 0) { async->munge_count += num_bytes; return num_bytes; }