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 7AEC2202963; Mon, 27 Oct 2025 19:06:45 +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=1761592005; cv=none; b=ceXiJnhQC8pX2V8Vt0o35yuFYRvZYwFepIO6iFInnR9V92Ox5WVb1Bp6p/zILswTNNZsTgP44gPVlWdd9Um9iqIgxf4oBWXyf7enxqxtffroiBpN0M6HTPzsahWcxtPZGXGEwMOENM31YsR/lWPL2k2PAx6kcfP+Wggk8x9nKFo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761592005; c=relaxed/simple; bh=ej2KkGEBD31qR+tbCg/Cnm9FfvP7SNgZItuhn7WQpNk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=QLpRaS158DHL0yK6sF9MB9WFV62A+gEE2gA+if5lyvp6zBe6bEyeZxQ3VO+z3mCNJCGyCbCBLMFZq39xD3hOfu5mByx2BWGTaqeEYNcQPGBcUCx3SIS1U43mF8AcKqUmt2mnTm7XCz4zoQZvIIEFeqsecBPuzi8quc2ztt/XwWw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ZZuUGLww; 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="ZZuUGLww" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0C9E0C4CEF1; Mon, 27 Oct 2025 19:06:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1761592005; bh=ej2KkGEBD31qR+tbCg/Cnm9FfvP7SNgZItuhn7WQpNk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZZuUGLwwapElZ/wp/kzLzoHRXnKGcP1DBUcodS3+Ora2JSF1BLas+XIOCA6QgLaD+ ZiFDAOAVIrxwS3hWgptAT1pyZ8r5p3ONjdxZY1Kk56q9iBkJDyXXMW64TYDpKZtZvY Dj4B6LntubFHk2e/7b4GHVZtpMcjIYEmrYziK8fs= 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 5.15 082/123] comedi: fix divide-by-zero in comedi_buf_munge() Date: Mon, 27 Oct 2025 19:36:02 +0100 Message-ID: <20251027183448.585126928@linuxfoundation.org> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20251027183446.381986645@linuxfoundation.org> References: <20251027183446.381986645@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 5.15-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 @@ -369,7 +369,7 @@ 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; }