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

[Cédric Le Goater]

On 3/21/25 10:47, Jamin Lin wrote:

Hi Cedric,

Subject: [PATCH v1 02/22] 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_...@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

Fixes: 5cd7d8564a8b563da724b9e6264c967f0a091afa ("aspeed/hace: Support AST2600 HACE 
")

Reviewed-by: Cédric Le Goater <c...@redhat.com>

Thanks,

C.