Re: [Qemu-devel] [PATCH] i2c: pm_smbus: check smb_index before block transfer write

[li qiang]

在 2018/12/6 16:48, P J P 写道:
> From: Prasad J Pandit <address@hidden>
>
> While performing block transfer write in smb_ioport_writeb(),
> 'smb_index' is incremented and used to index smb_data[] array.
> Check 'smb_index' value to avoid OOB access.
>
> Reported-by: Michael Hanselmann <address@hidden>
> Signed-off-by: Prasad J Pandit <address@hidden>
> ---
>   hw/i2c/pm_smbus.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/hw/i2c/pm_smbus.c b/hw/i2c/pm_smbus.c
> index 685a2378ed..03062740cc 100644
> --- a/hw/i2c/pm_smbus.c
> +++ b/hw/i2c/pm_smbus.c
> @@ -240,6 +240,9 @@ static void smb_ioport_writeb(void *opaque, hwaddr addr, 
> uint64_t val,
>               uint8_t read = s->smb_addr & 0x01;
>   
>               s->smb_index++;
> +            if (s->smb_index >= PM_SMBUS_MAX_MSG_SIZE) {
> +                s->smb_index = 0;
> +            }
>               if (!read && s->smb_index == s->smb_data0) {
>                   uint8_t prot = (s->smb_ctl >> 2) & 0x07;
>                   uint8_t cmd = s->smb_cmd;

Oh... Finally another one find this.....

I've already found this. This is very a serious security issue.

I have wrote a full exploit to make a VM escape using this vulnerability.

This guest can read/write a 4G memory of qemu process by default 
configuration.

As far as I know, this vulnerability may be the most serious 
vulnerability of the qemu history.

Please pay a lot of attention for this issue.

Later I will release the full paper and exploit. It's not harm as this 
is introduced in 3.1

and no one use it now.


Thanks,

Li Qiang