[PATCH v1 02/22] hw/misc/aspeed_hace: Fix buffer overflow in has_padding function

[Jamin Lin via <qemu-devel@nongnu.org>]

The maximum padding size is either 64 or 128 bytes and should always be smaller
than "req_len". If "padding_size" exceeds "req_len", then
"req_len - padding_size" underflows due to "uint32_t" data type, leading to a
large incorrect value (e.g., `0xFFXXXXXX`). This causes an out-of-bounds memory
access, potentially leading to a buffer overflow.

Added a check to ensure "padding_size" does not exceed "req_len" before
computing "pad_offset". This prevents "req_len - padding_size" from underflowing
and avoids accessing invalid memory.

Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
---
 hw/misc/aspeed_hace.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/misc/aspeed_hace.c b/hw/misc/aspeed_hace.c
index 8e7e8113a5..d8b5f048bb 100644
--- a/hw/misc/aspeed_hace.c
+++ b/hw/misc/aspeed_hace.c
@@ -128,6 +128,11 @@ static bool has_padding(AspeedHACEState *s, struct iovec *iov,
     if (*total_msg_len <= s->total_req_len) {
         uint32_t padding_size = s->total_req_len - *total_msg_len;
         uint8_t *padding = iov->iov_base;
+
+        if (padding_size > req_len) {
+            return false;
+        }
+
         *pad_offset = req_len - padding_size;
         if (padding[*pad_offset] == 0x80) {
             return true;
-- 
2.43.0