linux-kernel - Re: [PATCH 1/5 v4] accel/qaic: tighten bounds checking in encode

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Date:   Fri, 14 Jul 2023 17:11:18 +0530
From:   Pranjal Ramajor Asha Kanojiya <quic_pkanojiy@...cinc.com>
To:     Dan Carpenter <dan.carpenter@...aro.org>,
        Jeffrey Hugo <quic_jhugo@...cinc.com>
CC:     Carl Vanderlip <quic_carlv@...cinc.com>,
        Oded Gabbay <ogabbay@...nel.org>,
        Jacek Lawrynowicz <jacek.lawrynowicz@...ux.intel.com>,
        Stanislaw Gruszka <stanislaw.gruszka@...ux.intel.com>,
        <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <linux-kernel@...r.kernel.org>, <kernel-janitors@...r.kernel.org>
Subject: Re: [PATCH 1/5 v4] accel/qaic: tighten bounds checking in
 encode_message()



On 7/11/2023 1:50 PM, Dan Carpenter wrote:
> There are several issues in this code.  The check at the start of the
> loop:
> 
> 	if (user_len >= user_msg->len) {
> 
> This check does not ensure that we have enough space for the trans_hdr
> (8 bytes).  Instead the check needs to be:
> 
> 	if (user_len > user_msg->len - sizeof(*trans_hdr)) {
> 
> That subtraction is done as an unsigned long we want to avoid
> negatives.  Add a lower bound to the start of the function.
> 
> 	if (user_msg->len < sizeof(*trans_hdr))
> 
> There is a second integer underflow which can happen if
> trans_hdr->len is zero inside the encode_passthrough() function.
> 
> 	memcpy(out_trans->data, in_trans->data, in_trans->hdr.len - sizeof(in_trans->hdr));
> 
> Instead of adding a check to encode_passthrough() it's better to check
> in this central place.  Add that check:
> 
> 	if (trans_hdr->len < sizeof(trans_hdr)
> 
> The final concern is that the "user_len + trans_hdr->len" might have an
> integer overflow bug.  Use size_add() to prevent that.
> 
> -	if (user_len + trans_hdr->len > user_msg->len) {
> +	if (size_add(user_len, trans_hdr->len) > user_msg->len) {
> 
> Fixes: 129776ac2e38 ("accel/qaic: Add control path")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>

Reviewed-by: Pranjal Ramajor Asha Kanojiya <quic_pkanojiy@...cinc.com>