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 1DA7534321A for ; Thu, 21 Aug 2025 13:36:23 +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=1755783383; cv=none; b=q56YhJdWE0TRP8/Ta+mF9067e2XMEK+U7BngP+gAYCKSNe+zufDbDuJP3IAhu+VuFhNn6xthy6F2YzSHHS6fq2kXmmT0KqH5qbir2sKUJoZAuV1zIsauKf9GMBn2Bg8tgUsCj1l/jefUe6EtC1lFZAfNcIQ81XEX6rqqOitZHBs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755783383; c=relaxed/simple; bh=xU1L7uo+/yHtbJFkGvI0RjqjMMwJ0kl7L+pMiGc9fPE=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=a1uqa99sQUAa5w78c2xYvN3228W/Gwmf8YDvI7DEm1d2sEHYMkZHNah5EjcxCMN8F6fCkzDVrJBupAyvqLml4Zz6YsZQtJcS/aHpxwN94UBmnLiby90qhOyDOCiJ06RIg4vydEW2AR9qJpu3HXvWvER6uEjAB4ED1CnXS3pZCAo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=e5Km9CFX; 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="e5Km9CFX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7F263C4CEEB; Thu, 21 Aug 2025 13:36:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1755783383; bh=xU1L7uo+/yHtbJFkGvI0RjqjMMwJ0kl7L+pMiGc9fPE=; h=Subject:To:Cc:From:Date:From; b=e5Km9CFXrygIB3iqgBsJ3CztHbw+qr7Hl62iAmeEf2kVTvh/Yz6syReFgivNfxWOw SHnClaiWQ9L+bU+JQZnXaCLAVqj0i2Di09Qjo7L/ovy15FtQrVRsTYXP72ucfWD9q0 1L1/deIMNYTyEzE6kgRTuSlOAS2wnPmEJf+xLdF8= Subject: FAILED: patch "[PATCH] media: rainshadow-cec: fix TOCTOU race condition in" failed to apply to 5.4-stable tree To: hanguidong02@gmail.com,hverkuil@xs4all.nl Cc: From: Date: Thu, 21 Aug 2025 15:36:20 +0200 Message-ID: <2025082119-december-ranking-b3a3@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y git checkout FETCH_HEAD git cherry-pick -x 7af160aea26c7dc9e6734d19306128cce156ec40 # git commit -s git send-email --to '' --in-reply-to '2025082119-december-ranking-b3a3@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 7af160aea26c7dc9e6734d19306128cce156ec40 Mon Sep 17 00:00:00 2001 From: Gui-Dong Han Date: Fri, 6 Jun 2025 03:04:59 +0000 Subject: [PATCH] media: rainshadow-cec: fix TOCTOU race condition in rain_interrupt() In the interrupt handler rain_interrupt(), the buffer full check on rain->buf_len is performed before acquiring rain->buf_lock. This creates a Time-of-Check to Time-of-Use (TOCTOU) race condition, as rain->buf_len is concurrently accessed and modified in the work handler rain_irq_work_handler() under the same lock. Multiple interrupt invocations can race, with each reading buf_len before it becomes full and then proceeding. This can lead to both interrupts attempting to write to the buffer, incrementing buf_len beyond its capacity (DATA_SIZE) and causing a buffer overflow. Fix this bug by moving the spin_lock() to before the buffer full check. This ensures that the check and the subsequent buffer modification are performed atomically, preventing the race condition. An corresponding spin_unlock() is added to the overflow path to correctly release the lock. This possible bug was found by an experimental static analysis tool developed by our team. Fixes: 0f314f6c2e77 ("[media] rainshadow-cec: new RainShadow Tech HDMI CEC driver") Cc: stable@vger.kernel.org Signed-off-by: Gui-Dong Han Signed-off-by: Hans Verkuil diff --git a/drivers/media/cec/usb/rainshadow/rainshadow-cec.c b/drivers/media/cec/usb/rainshadow/rainshadow-cec.c index ee870ea1a886..6f8d6797c614 100644 --- a/drivers/media/cec/usb/rainshadow/rainshadow-cec.c +++ b/drivers/media/cec/usb/rainshadow/rainshadow-cec.c @@ -171,11 +171,12 @@ static irqreturn_t rain_interrupt(struct serio *serio, unsigned char data, { struct rain *rain = serio_get_drvdata(serio); + spin_lock(&rain->buf_lock); if (rain->buf_len == DATA_SIZE) { + spin_unlock(&rain->buf_lock); dev_warn_once(rain->dev, "buffer overflow\n"); return IRQ_HANDLED; } - spin_lock(&rain->buf_lock); rain->buf_len++; rain->buf[rain->buf_wr_idx] = data; rain->buf_wr_idx = (rain->buf_wr_idx + 1) & 0xff;