From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (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 E6045339398; Thu, 20 Aug 2026 12:57:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787230660; cv=none; b=OD4c8KQW9WGpu1mWsAxNrdUG1ys3oESTxbEo0XHbFsJu16DatFN3p63UCNuVIPU0ArmkvtKJ5lVkvY6NjeLfrNU8ToBq6KjgbLjTSeYJ5wVrxE023KP5Fnn12yP/Hbc24CUGSPxHfBKUa/ab52HeNGVwN5W4A5Nvy6wFIavyQT4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787230660; c=relaxed/simple; bh=NBURnJ/h8jK40DD3L0sAXfodvA9mcG66XWuTjw7j+b0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=XD/GndM22teUkI6b3AZkqkm6w3lxrRy5YZo8E8+BdM5kxuFqr4hDfOVxLPY4TGjCPc0OBPzbN1lXqWW5YJ0HI49kPyhZ3Qq0ycwWb1RDWO05KU7AKu/Aj8X6guKwvphxAcxpWD6zgGT2AFuiVCz5o7w1jOEMpA4kw/aa1FA4XKY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=iunfu5DJ; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="iunfu5DJ" Received: from ideasonboard.com (mob-109-113-29-237.net.vodafone.it [109.113.29.237]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 23EDE492; Thu, 20 Aug 2026 14:56:14 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1787230574; bh=NBURnJ/h8jK40DD3L0sAXfodvA9mcG66XWuTjw7j+b0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=iunfu5DJAfG2Ho2eUUeKR+7z8rrxdDN8kfPfJgIFcwoBq9cz8YlhcmN3NZuiIYy4k sBVqz6OnRbUiI2b8l/ce4A6qLxFyaVzIKfi18GxxVmu5kQtwZDbl0NoQySc81KDY9h f7IWASQVPEZ0UNek04eIeC1RVfOghNYhbNwFEGD4= Date: Thu, 20 Aug 2026 14:57:32 +0200 From: Jacopo Mondi To: David Carlier Cc: Jacopo Mondi , Laurent Pinchart , Mauro Carvalho Chehab , linux-media@vger.kernel.org, stable@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] media: v4l2-isp: reject zero-sized parameter blocks Message-ID: References: <20260820111722.1233915-1-devnexen@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260820111722.1233915-1-devnexen@gmail.com> Hi David On Thu, Aug 20, 2026 at 12:17:22PM +0100, David Carlier wrote: > v4l2_isp_params_validate_buffer() walks the blocks of a parameters > buffer by adding block->size to the current offset, but never bounds > that size from below. A block with size 0 is not caught by the > block->size > buffer_size test, and the comparison against info->size > passes as well when the driver's type_info[] entry is an uninitialised > hole, both sizes being 0. The walk then makes no forward progress and > loops forever. > > Drivers build their type_info[] arrays with designated initialisers > indexed by their block type enumeration, so an enumerator left without > an entry leaves a zeroed hole rather than failing the build. Drivers > call the validator from vb2 .buf_prepare, so such a hole turns a > VIDIOC_QBUF on the parameters video device into an unkillable task > spinning with the queue mutex held. > > Reject a block smaller than its own header. A block's size includes its > header, so anything below that is malformed whatever the driver table > contains, and rejecting it is what keeps the walk moving. Blocks > carrying only a header to disable a block are exactly that size and > still pass. > > An empty type info entry can then no longer stall the walk, but a block > matched against it is only constrained by that header size check. Reject > such a block explicitly: the driver does not implement the type and > cannot tell whether the block content is meaningful, and accepting it > silently would leave that content unconstrained until a later kernel > implements the type and starts validating it. > > Fixes: 3cb6de6fafb8 ("media: v4l2-core: Introduce v4l2-isp.c") > Cc: stable@vger.kernel.org > Suggested-by: Jacopo Mondi > Signed-off-by: David Carlier > --- > v3: > - reject a block whose type info entry is empty instead of skipping > it, so a type the driver does not implement cannot become > unconstrained uAPI (Jacopo) > > v2: > - skip an empty type info entry instead of matching the block against > a zeroed one > - reworded the commit message, which no longer leans on rppx1 > > drivers/media/v4l2-core/v4l2-isp.c | 22 +++++++++++++++++++++- > 1 file changed, 21 insertions(+), 1 deletion(-) > > diff --git a/drivers/media/v4l2-core/v4l2-isp.c b/drivers/media/v4l2-core/v4l2-isp.c > index 1eb46e080afa..efe994b4c4d7 100644 > --- a/drivers/media/v4l2-core/v4l2-isp.c > +++ b/drivers/media/v4l2-core/v4l2-isp.c > @@ -84,6 +84,13 @@ int v4l2_isp_params_validate_buffer(struct device *dev, struct vb2_buffer *vb, > return -EINVAL; > } > > + if (block->size < sizeof(*block)) { > + dev_dbg(dev, > + "Invalid block size %u at offset %zu\n", > + block->size, block_offset); > + return -EINVAL; > + } > + I'm sorry, but now that we refuse empty block info with size == 0, wouldn't this be caught by the below if (block->size != info->size && (!(block->flags & V4L2_ISP_PARAMS_FL_BLOCK_DISABLE) || block->size != sizeof(*block))) { Do we need to check it here as well ? nit: the dev_dbg() line fits on 2 lines only. > if (block->size > buffer_size) { > dev_dbg(dev, "Premature end of parameters data\n"); > return -EINVAL; > @@ -99,12 +106,25 @@ int v4l2_isp_params_validate_buffer(struct device *dev, struct vb2_buffer *vb, > return -EINVAL; > } > > + /* > + * An empty type info entry denotes a block type the driver > + * does not support. Reject the buffer instead of ignoring the > + * block: accepting it silently would let userspace fill it > + * with data that a later kernel, once it implements the type, > + * would validate and possibly reject. > + */ > + info = &type_info[block->type]; > + if (!info->size) { > + dev_dbg(dev, "Unsupported block type %u at offset %zu\n", > + block->type, block_offset); > + return -EINVAL; > + } > + > /* > * Match the block reported size against the type info provided > * one, but allow the block to only contain the header in > * case it is going to be disabled. > */ > - info = &type_info[block->type]; > if (block->size != info->size && > (!(block->flags & V4L2_ISP_PARAMS_FL_BLOCK_DISABLE) || > block->size != sizeof(*block))) { > -- > 2.55.0 >