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

[Philippe Mathieu-Daudé]

Hi Zheyu,

On 18/6/24 17:23, Zheyu Ma wrote:
> 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");

Usually hardware doesn't "adjust" but report error earlier.

> +        len = s->size - offset;
> +    }
> +
>       trace_m25p80_flash_erase(s, offset, len);
>   
>       if ((s->pi->flags & capa_to_assert) != capa_to_assert) {