[PATCH] block: m25p80: Fix heap-buffer-overflow in flash_erase function

[Zheyu Ma <zheyuma97@gmail.com>]

This patch fixes a heap-buffer-overflow issue in the flash_erase function
of the m25p80 flash memory emulation. The overflow occurs when the
combination of offset and length exceeds the allocated memory for the
storage. The patch adds a check to ensure that the erase length does not
exceed the storage size and adjusts the length accordingly if necessary.

Reproducer:
cat << EOF | qemu-system-aarch64 -display none \
-machine accel=qtest, -m 512M -machine kudo-bmc -qtest stdio
writeq 0xc0000010 0x6
writel 0xc000000c 0x9
writeq 0xc0000010 0xf27f9412
writeq 0xc000000f 0x2b5cdc26
writeq 0xc000000c 0xffffffffffffffff
writeq 0xc000000c 0xffffffffffffffff
writeq 0xc000000c 0xffffffffffffffff
writel 0xc000000c 0x9
writeq 0xc000000c 0x9
EOF

ASan log:
==2614308==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x7fd3fb7fc000 at pc 0x55aa77a442dc bp 0x7fffaa155900 sp 0x7fffaa1550c8
WRITE of size 65536 at 0x7fd3fb7fc000 thread T0
    #0 0x55aa77a442db in __asan_memset llvm/compiler-rt/lib/asan/asan_interceptors_memintrinsics.cpp:26:3
    #1 0x55aa77e7e6b3 in flash_erase hw/block/m25p80.c:631:5
    #2 0x55aa77e6f8b1 in complete_collecting_data hw/block/m25p80.c:773:9
    #3 0x55aa77e6aaa9 in m25p80_transfer8 hw/block/m25p80.c:1550:13
    #4 0x55aa78e9a691 in ssi_transfer_raw_default hw/ssi/ssi.c:92:16
    #5 0x55aa78e996c0 in ssi_transfer hw/ssi/ssi.c:165:14
    #6 0x55aa78e8d76a in npcm7xx_fiu_uma_transaction hw/ssi/npcm7xx_fiu.c:336:9
    #7 0x55aa78e8be4b in npcm7xx_fiu_ctrl_write hw/ssi/npcm7xx_fiu.c:428:13

Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
---
 hw/block/m25p80.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/hw/block/m25p80.c b/hw/block/m25p80.c
index 8dec134832..e9a59f6616 100644
--- a/hw/block/m25p80.c
+++ b/hw/block/m25p80.c
@@ -617,6 +617,12 @@ static void flash_erase(Flash *s, int offset, FlashCMD cmd)
         abort();
     }
 
+    if (offset + len > s->size) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "M25P80: Erase exceeds storage size, adjusting length\n");
+        len = s->size - offset;
+    }
+
     trace_m25p80_flash_erase(s, offset, len);
 
     if ((s->pi->flags & capa_to_assert) != capa_to_assert) {
-- 
2.34.1