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 DD13B10E0; Tue, 26 Aug 2025 14:43:10 +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=1756219391; cv=none; b=fLHYGYIqXTzvUeeOtV+h/3Mxrih+DMlw6ZkE3wm1jgtbpYZKX9MbImPY0elss4DPgAjIA/OoT8OSpXDoQv/WwgC5XJx44cCE+Nhk9k11CQWb4d+5ckdDJGW6CqDzByV+fMeK5CoL2mTB6ivq5OHP1vnT/fJmbBOKxYUFV6vyaqc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756219391; c=relaxed/simple; bh=ztdUQUC9dWSrglNOQ3Yj98rMqhRmiuClbjiWfRrm/EM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=C8Ybl4OMGMsPCw1Pgb1AE5Mlmwv8h+pFgvWCb51U3gXL6U0uCV6hn/UnTHPhTnQgDlT9Js9IDjuHB6tQJe65sUX1HOe1kdp0/x4k1HC1FmaJ5VVk8gCHqZ6vN/H1I0shdzZJVBmrNEso0rRwxkh5k7q4b7+xhLKGjThj7qO9RAo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=J73K5rqB; 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="J73K5rqB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6A116C4CEF1; Tue, 26 Aug 2025 14:43:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1756219390; bh=ztdUQUC9dWSrglNOQ3Yj98rMqhRmiuClbjiWfRrm/EM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=J73K5rqBtghwhLDptZvbQfTjI2R0E+Tdm6/zT/JFqzPDGmw0twOo3s7d649MFTf1F /Q8qB8m408SutOy/M74nTLYegfiFQ0KXryufaxeKn8/TnF8HX2Mq0B7+847czcwQE7 a4UkIkojNYW+xW9OoFKvXroMBxb8eyWYapq0HEqM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Gui-Dong Han , Hans Verkuil , Sasha Levin Subject: [PATCH 5.4 364/403] media: rainshadow-cec: fix TOCTOU race condition in rain_interrupt() Date: Tue, 26 Aug 2025 13:11:30 +0200 Message-ID: <20250826110917.056343183@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250826110905.607690791@linuxfoundation.org> References: <20250826110905.607690791@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 5.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gui-Dong Han [ Upstream commit 7af160aea26c7dc9e6734d19306128cce156ec40 ] 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 [ drivers/media/cec/usb/rainshadow/ => drivers/media/usb/rainshadow-cec/ ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/media/usb/rainshadow-cec/rainshadow-cec.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/drivers/media/usb/rainshadow-cec/rainshadow-cec.c +++ b/drivers/media/usb/rainshadow-cec/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;