hw/misc/aspeed_hace: Fix buffer overflow in has_padding function

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>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Fixes: 5cd7d8564a8b563da724b9e6264c967f0a091afa ("aspeed/hace: Support AST2600 HACE ")
Link: https://lore.kernel.org/qemu-devel/20250321092623.2097234-3-jamin_lin@aspeedtech.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
(cherry picked from commit 78877b2e06464f49f777e086845e094ea7bc82ef)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

diff --git a/hw/misc/aspeed_hace.c b/hw/misc/aspeed_hace.c
index 69175e972da2b6bdbac2147595e17dd8dc3663cb..11bd25708e0edc975f9b93b04fa318230d522bc9 100644 (file)
--- a/hw/misc/aspeed_hace.c
+++ b/hw/misc/aspeed_hace.c
@@ -123,6 +123,11 @@ 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;