[PATCH 2/2] aspeed/hace: Prevent total_req_len overflow

["Cédric Le Goater" <clg@redhat.com>]

In accumulate mode, total_req_len is incremented with plen (hwaddr)
for each hash request. Repeated additions can overflow total_req_len
(uint32_t) and potentially bypass validation checks in has_padding().

Add a helper function to detect overflow before incrementing
total_req_len and reject the request if overflow would occur.

Reported-by: Katherine Leaver <katherine.j.leaver@gmail.com>
Cc: qemu-stable@nongnu.org
Fixes: 5cd7d8564a8b ("aspeed/hace: Support AST2600 HACE")
Signed-off-by: Cédric Le Goater <clg@redhat.com>
---
 hw/misc/aspeed_hace.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/hw/misc/aspeed_hace.c b/hw/misc/aspeed_hace.c
index ef698b3ecb72..0504d61cbf0a 100644
--- a/hw/misc/aspeed_hace.c
+++ b/hw/misc/aspeed_hace.c
@@ -205,6 +205,19 @@ static uint64_t hash_get_source_addr(AspeedHACEState *s)
     return src_addr;
 }
 
+static bool hash_accumulate_len(AspeedHACEState *s, hwaddr plen)
+{
+    if (plen > UINT32_MAX - s->total_req_len) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "%s: total_req_len overflow, current=0x%x, adding=0x%"
+                      HWADDR_PRIx "\n", __func__, s->total_req_len, plen);
+        return false;
+    }
+
+    s->total_req_len += plen;
+    return true;
+}
+
 static int hash_prepare_direct_iov(AspeedHACEState *s, struct iovec *iov,
                                    bool acc_mode, bool *acc_final_request)
 {
@@ -232,7 +245,9 @@ static int hash_prepare_direct_iov(AspeedHACEState *s, struct iovec *iov,
     iov_idx = 1;
 
     if (acc_mode) {
-        s->total_req_len += plen;
+        if (!hash_accumulate_len(s, plen)) {
+            return -1;
+        }
 
         if (has_padding(s, &iov[0], plen, &total_msg_len,
                         &pad_offset)) {
@@ -299,7 +314,9 @@ static int hash_prepare_sg_iov(AspeedHACEState *s, struct iovec *iov,
 
         iov[iov_idx].iov_base = haddr;
         if (acc_mode) {
-            s->total_req_len += plen;
+            if (!hash_accumulate_len(s, plen)) {
+                return -1;
+            }
 
             if (has_padding(s, &iov[iov_idx], plen, &total_msg_len,
                             &pad_offset)) {
-- 
2.54.0