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 03F0B238C0B; Tue, 26 Aug 2025 13:06:41 +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=1756213602; cv=none; b=fIIcBnRKiuZQoa6QkCfVO69lq5n9MSp9gJXo0RqzoAFxuqA6VvE2AhuctA8Zzw0haGhkPcGMevBcd0WkNHOFRdJ2BCNk488IlBJyR289RzhjNYCYJFhW5idma1/UDL3uCPfuR05xN0HLRp5eBcqBWXhC+SnHysBQjd1ibeBNQEg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756213602; c=relaxed/simple; bh=A4JH7ru4QuVWq+Ye4aeqKpPPZmKzBRoswaj8ITBe6B8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uldA+fNeKZ08Fe3iKW3rCdEfiSYA0wlDzyf8gD33eu5f+dR2iL0Jw6oFquuQfu2xBjemBmUdbS6NCSssgnPbyJR0Ane4/OtC29aHSdXRoNYwpMUXhTaLYDYrnezzRfOd45bxV2n1OYcv1Sjli2o662n/ir3oihDAWsnxbWAL1xE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=F6m/SUxA; 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="F6m/SUxA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7F5EBC4CEF1; Tue, 26 Aug 2025 13:06:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1756213601; bh=A4JH7ru4QuVWq+Ye4aeqKpPPZmKzBRoswaj8ITBe6B8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=F6m/SUxA/wj5f3R769OcLqCSOBk52Tt/vMX9SF8+PNtKbESQoqNYmIknN5gtU2MfS rWiyyyZWVhpwvL+8xU3nYiDBnDhlg3un4nSCBPrldE2vYX9IS+wNYiwg9RPnaHujLs cBsK+n2VCXWXOPVc4bYTOh7/cNf3DO3Gsu5uUbHE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Gui-Dong Han , Hans Verkuil Subject: [PATCH 6.6 408/587] media: rainshadow-cec: fix TOCTOU race condition in rain_interrupt() Date: Tue, 26 Aug 2025 13:09:17 +0200 Message-ID: <20250826111003.308108279@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250826110952.942403671@linuxfoundation.org> References: <20250826110952.942403671@linuxfoundation.org> User-Agent: quilt/0.68 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 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gui-Dong Han commit 7af160aea26c7dc9e6734d19306128cce156ec40 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- drivers/media/cec/usb/rainshadow/rainshadow-cec.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- 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 { 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;