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 644784C3CC; Mon, 8 Jan 2024 15:09:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="mRteBajX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BEB34C433CB; Mon, 8 Jan 2024 15:09:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1704726597; bh=qx9SM/VZjVHhI97D50uUpQLSDto2roBKMI86wBGK0ac=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mRteBajXTyUpq8vW69xIworemvXXni9yeah84HaSoSH74P8o0smhJ0kv8xdvYv1mb lwQok+oblFa3NKTcQVvRUxKWtP363zR2IY48p9MpW5m+xINIvcKGTWri5nmRFj+Yu6 mdaxN6hJYe3yZyCwmALZC0ttvIju+64jbP//0UTo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Stephen Boyd , Guenter Roeck , Douglas Anderson , Sasha Levin Subject: [PATCH 6.6 018/124] drm/bridge: parade-ps8640: Never store more than msg->size bytes in AUX xfer Date: Mon, 8 Jan 2024 16:07:24 +0100 Message-ID: <20240108150603.816004448@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240108150602.976232871@linuxfoundation.org> References: <20240108150602.976232871@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org 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: Douglas Anderson [ Upstream commit 3164c8a70073d43629b4e11e083d3d2798f7750f ] While testing, I happened to notice a random crash that looked like: Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: drm_dp_dpcd_probe+0x120/0x120 Analysis of drm_dp_dpcd_probe() shows that we pass in a 1-byte buffer (allocated on the stack) to the aux->transfer() function. Presumably if the aux->transfer() writes more than one byte to this buffer then we're in a bad shape. Dropping into kgdb, I noticed that "aux->transfer" pointed at ps8640_aux_transfer(). Reading through ps8640_aux_transfer(), I can see that there are cases where it could write more bytes to msg->buffer than were specified by msg->size. This could happen if the hardware reported back something bogus to us. Let's fix this so we never write more than msg->size bytes. We'll still read all the bytes from the hardware just in case the hardware requires it since the aux transfer data comes through an auto-incrementing register. NOTE: I have no actual way to reproduce this issue but it seems likely this is what was happening in the crash I looked at. Fixes: 13afcdd7277e ("drm/bridge: parade-ps8640: Add support for AUX channel") Reviewed-by: Stephen Boyd Reviewed-by: Guenter Roeck Signed-off-by: Douglas Anderson Link: https://patchwork.freedesktop.org/patch/msgid/20231214123752.v3.1.I9d1afcaad76a3e2c0ca046dc4adbc2b632c22eda@changeid Signed-off-by: Sasha Levin --- drivers/gpu/drm/bridge/parade-ps8640.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c index 8161b1a1a4b12..d264b80d909de 100644 --- a/drivers/gpu/drm/bridge/parade-ps8640.c +++ b/drivers/gpu/drm/bridge/parade-ps8640.c @@ -330,11 +330,12 @@ static ssize_t ps8640_aux_transfer_msg(struct drm_dp_aux *aux, return ret; } - buf[i] = data; + if (i < msg->size) + buf[i] = data; } } - return len; + return min(len, msg->size); } static ssize_t ps8640_aux_transfer(struct drm_dp_aux *aux, -- 2.43.0