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 6F2312F25F1; Mon, 27 Oct 2025 19:23:53 +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=1761593033; cv=none; b=LDf2oKm3UJ5m/wOafRk/NmcVMCUIuwvNv1o0H80VHzoFAQzrUJO+CcGMqheFSzPqOTLmeePE2PJNJeCV40Igj3SZbpFe77cp4j8b07C4TsrkwUauBdlfpnLmrgPabJsnpQrlQGyNbMXpVvg+ES4/szxLbTPLCMDpf7h9V2DSogc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761593033; c=relaxed/simple; bh=o8XaPq5qDjaNYUnrZFQErK4xW2F6KoO3jbPh6BZkH54=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=jzRhVWr8boRoq1YNxawM31J95bTMugiYJE77NX3uCkQsxnnS+bxbsSnAqzf96kddA5de2I6qGHWsVaSC00ztiVjvUJSJM4ys4WBX8e1xJKfOSlgnq38MPzDhBUi63X8eM20wtzKW45aLPgDESiq43IljDA91LTr/A9OU6Gt0rPI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=VoglarWD; 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="VoglarWD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 03B86C4CEF1; Mon, 27 Oct 2025 19:23:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1761593033; bh=o8XaPq5qDjaNYUnrZFQErK4xW2F6KoO3jbPh6BZkH54=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VoglarWDYJuJtyYFgvMaxdwOD0N4knEKI+tBAqqqVV05RIRyl/uXYeevS6N+fZqBJ OvDxcccTcyg78suPP3t3/3CTDaWL90HCanUyXWsIg2b2WEkDmQf3KH6VP3W1HBTRJn 461SFk0cDMrIaolF3FIAPIU3JxOH22WU2C/e09FY= 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 6.12 103/117] comedi: fix divide-by-zero in comedi_buf_munge() Date: Mon, 27 Oct 2025 19:37:09 +0100 Message-ID: <20251027183456.807622715@linuxfoundation.org> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20251027183453.919157109@linuxfoundation.org> References: <20251027183453.919157109@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-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; }