[PATCH 1/5 v4] accel/qaic: tighten bounds checking in encode_message()

[Dan Carpenter]

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.carpen...@linaro.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