Re: [PATCH 2/5] accel/qaic: tighten bounds checking in decode_message()

[Pranjal Ramajor Asha Kanojiya]

On 6/21/2023 12:51 PM, Dan Carpenter wrote:
Copy the bounds checking from encode_message() to decode_message().

This patch addresses the following concerns.  Ensure that there is
enough space for at least one header so that we don't have a negative
size later.

        if (msg_hdr_len < sizeof(*trans_hdr))

Ensure that we have enough space to read the next header from the
msg->data.

        if (msg_len >= msg_hdr_len - sizeof(*trans_hdr))
                return -EINVAL;

Check that the trans_hdr->len is not below the minimum size:

        if (hdr_len < sizeof(*trans_hdr))

This minimum check ensures that we don't corrupt memory in
decode_passthrough() when we do.

        memcpy(out_trans->data, in_trans->data, len - sizeof(in_trans->hdr));

And finally, use size_add() to prevent an integer overflow:

        if (size_add(msg_len, hdr_len) > msg_hdr_len)

Fixes: 129776ac2e38 ("accel/qaic: Add control path")
Signed-off-by: Dan Carpenter <dan.carpen...@linaro.org>
---
  drivers/accel/qaic/qaic_control.c | 12 ++++++++++--
  1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/accel/qaic/qaic_control.c 
b/drivers/accel/qaic/qaic_control.c
index a51b1594dcfa..78f6c3d6380d 100644
--- a/drivers/accel/qaic/qaic_control.c
+++ b/drivers/accel/qaic/qaic_control.c
@@ -955,15 +955,23 @@ static int decode_message(struct qaic_device *qdev, 
struct manage_msg *user_msg,
        int ret;
        int i;
  
-	if (msg_hdr_len > QAIC_MANAGE_MAX_MSG_LENGTH)
+       if (msg_hdr_len < sizeof(*trans_hdr) ||
+           msg_hdr_len > QAIC_MANAGE_MAX_MSG_LENGTH)
                return -EINVAL;
  
  	user_msg->len = 0;
        user_msg->count = le32_to_cpu(msg->hdr.count);
  
  	for (i = 0; i < user_msg->count; ++i) {
+               u32 hdr_len;
+
+               if (msg_len >= msg_hdr_len - sizeof(*trans_hdr))
+                       return -EINVAL;
If I understand correctly this check is added to verify if we are left 
with trans_hdr size of data. In that case '>' comparison operator should 
be used.
+
                trans_hdr = (struct wire_trans_hdr *)(msg->data + msg_len);
-               if (msg_len + le32_to_cpu(trans_hdr->len) > msg_hdr_len)
+               hdr_len = le32_to_cpu(trans_hdr->len);
+               if (hdr_len < sizeof(*trans_hdr) ||
+                   size_add(msg_len, hdr_len) > msg_hdr_len)
                        return -EINVAL;
  
  		switch (le32_to_cpu(trans_hdr->type)) {