[PATCH v1 1/1] hw/misc/aspeed_sbc: Add bounds checking for OTP write operations

[Kane Chen <kane_chen@aspeedtech.com>]

There is a mismatch between the Aspeed OTP model and the Aspeed SBC
model in how the guest-provided address is handled.
aspeed_sbc_otp_prog() passes a word-indexed address directly
to address_space_write() without converting it to a byte offset,
whereas aspeed_otp_write() expects a byte offset and applies an
additional shift (otp_addr << 2). This double-shift confusion means
that an out-of-range word address can lead to a write beyond the
allocated storage.

Fix this by adding bounds checking on the word offset before
converting to byte offset and passing to address_space_write().
This matches the existing bounds check in aspeed_sbc_otp_read().

Cc: Kane-Chen-AS <kane_chen@aspeedtech.com>
Cc: qemu-stable@nongnu.org
Fixes: 1a00754ccf15 ("hw/misc: Add Aspeed Secure Boot Controller model")
Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3436
Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Kane-Chen-AS <kane_chen@aspeedtech.com>
---
 hw/misc/aspeed_sbc.c  | 14 +++++++++++---
 hw/nvram/aspeed_otp.c | 13 ++++++-------
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/hw/misc/aspeed_sbc.c b/hw/misc/aspeed_sbc.c
index 065e822e70..8b74dca13c 100644
--- a/hw/misc/aspeed_sbc.c
+++ b/hw/misc/aspeed_sbc.c
@@ -159,13 +159,21 @@ static bool aspeed_sbc_otp_prog(AspeedSBCState *s,
     MemTxResult ret;
     AspeedOTPState *otp = &s->otp;
     uint32_t value = s->regs[R_CAMP1];
+    uint32_t otp_offset = otp_addr << 2;
 
-    ret = address_space_write(&otp->as, otp_addr, MEMTXATTRS_UNSPECIFIED,
-                        &value, sizeof(value));
+    if (otp_addr >= OTP_TOTAL_DWORD_COUNT) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "Invalid OTP addr 0x%x\n",
+                      otp_addr);
+        return false;
+    }
+
+    ret = address_space_write(&otp->as, otp_offset, MEMTXATTRS_UNSPECIFIED,
+                              &value, sizeof(value));
     if (ret != MEMTX_OK) {
         qemu_log_mask(LOG_GUEST_ERROR,
                       "Failed to write OTP memory, addr = %x\n",
-                      otp_addr);
+                      otp_offset);
         return false;
     }
 
diff --git a/hw/nvram/aspeed_otp.c b/hw/nvram/aspeed_otp.c
index a60289000c..1a9d3841b8 100644
--- a/hw/nvram/aspeed_otp.c
+++ b/hw/nvram/aspeed_otp.c
@@ -57,12 +57,12 @@ static bool valid_program_data(uint32_t otp_addr,
     return has_programmable_bits != 0;
 }
 
-static bool program_otpmem_data(void *opaque, uint32_t otp_addr,
+static bool program_otpmem_data(void *opaque, hwaddr otp_offset,
                              uint32_t prog_bit, uint32_t *value)
 {
     AspeedOTPState *s = opaque;
+    uint32_t otp_addr = otp_offset >> 2;
     bool is_odd = otp_addr & 1;
-    uint32_t otp_offset = otp_addr << 2;
 
     memcpy(value, s->storage + otp_offset, sizeof(uint32_t));
 
@@ -79,26 +79,25 @@ static bool program_otpmem_data(void *opaque, uint32_t otp_addr,
     return true;
 }
 
-static void aspeed_otp_write(void *opaque, hwaddr otp_addr,
+static void aspeed_otp_write(void *opaque, hwaddr otp_offset,
                                 uint64_t val, unsigned size)
 {
     AspeedOTPState *s = opaque;
-    uint32_t otp_offset, value;
+    uint32_t value;
 
-    if (!program_otpmem_data(s, otp_addr, val, &value)) {
+    if (!program_otpmem_data(s, otp_offset, val, &value)) {
         qemu_log_mask(LOG_GUEST_ERROR,
                       "%s: Failed to program data, value = %x, bit = %"PRIx64"\n",
                       __func__, value, val);
         return;
     }
 
-    otp_offset = otp_addr << 2;
     memcpy(s->storage + otp_offset, &value, size);
 
     if (s->blk) {
         if (blk_pwrite(s->blk, otp_offset, size, &value, 0) < 0) {
             qemu_log_mask(LOG_GUEST_ERROR,
-                          "%s: Failed to write %x to %x\n",
+                          "%s: Failed to write %x to %"HWADDR_PRIx"\n",
                           __func__, value, otp_offset);
 
             return;
-- 
2.43.0