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

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Date:   Tue, 11 Jul 2023 11:20:44 +0300
From:   Dan Carpenter <dan.carpenter@...aro.org>
To:     Jeffrey Hugo <quic_jhugo@...cinc.com>
Cc:     Carl Vanderlip <quic_carlv@...cinc.com>,
        Pranjal Ramajor Asha Kanojiya <quic_pkanojiy@...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: [PATCH 1/5 v4] accel/qaic: tighten bounds checking in
 encode_message()

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>
---
v4: send this patch.
v2: * Fix the >= vs > bug in:

	if (user_len > user_msg->len - sizeof(*trans_hdr)) {

    * include overflow.h
---
 drivers/accel/qaic/qaic_control.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/accel/qaic/qaic_control.c b/drivers/accel/qaic/qaic_control.c
index 5c57f7b4494e..2fdd5959c52f 100644
--- a/drivers/accel/qaic/qaic_control.c
+++ b/drivers/accel/qaic/qaic_control.c
@@ -14,6 +14,7 @@
 #include <linux/mm.h>
 #include <linux/moduleparam.h>
 #include <linux/mutex.h>
+#include <linux/overflow.h>
 #include <linux/pci.h>
 #include <linux/scatterlist.h>
 #include <linux/types.h>
@@ -748,7 +749,8 @@ static int encode_message(struct qaic_device *qdev, struct manage_msg *user_msg,
 	int ret;
 	int i;
 
-	if (!user_msg->count) {
+	if (!user_msg->count ||
+	    user_msg->len < sizeof(*trans_hdr)) {
 		ret = -EINVAL;
 		goto out;
 	}
@@ -765,12 +767,13 @@ static int encode_message(struct qaic_device *qdev, struct manage_msg *user_msg,
 	}
 
 	for (i = 0; i < user_msg->count; ++i) {
-		if (user_len >= user_msg->len) {
+		if (user_len > user_msg->len - sizeof(*trans_hdr)) {
 			ret = -EINVAL;
 			break;
 		}
 		trans_hdr = (struct qaic_manage_trans_hdr *)(user_msg->data + user_len);
-		if (user_len + trans_hdr->len > user_msg->len) {
+		if (trans_hdr->len < sizeof(trans_hdr) ||
+		    size_add(user_len, trans_hdr->len) > user_msg->len) {
 			ret = -EINVAL;
 			break;
 		}
-- 
2.39.2