On 11/11/21 19:08, Klaus Jensen wrote:
> On Nov 11 16:31, Philippe Mathieu-Daudé wrote:
>> Both 'buf_len' and 'off' arguments are under guest control.
>> Since nvme_c2h() doesn't check out of boundary access, the
>> caller must check for eventual buffer overrun on 'trans_len'.
>>
>> Cc: qemu-sta...@nongnu.org
>> Reported-by: Qiuhao Li <qiuhao...@outlook.com>
>> Fixes: f432fdfa121 ("support changed namespace asynchronous event")
>> Signed-off-by: Philippe Mathieu-Daudé <phi...@redhat.com>
>> ---
>> hw/nvme/ctrl.c | 22 ++++++++++++----------
>> 1 file changed, 12 insertions(+), 10 deletions(-)
>>
>> diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
>> index 6a571d18cfa..634b290e069 100644
>> --- a/hw/nvme/ctrl.c
>> +++ b/hw/nvme/ctrl.c
>> @@ -4072,7 +4072,8 @@ static uint16_t nvme_smart_info(NvmeCtrl *n, uint8_t
>> rae, uint32_t buf_len,
>> NvmeNamespace *ns;
>> time_t current_ms;
>>
>> - if (off >= sizeof(smart)) {
>> + trans_len = MIN(sizeof(smart) - off, buf_len);
>> + if (trans_len >= sizeof(smart)) {
>> return NVME_INVALID_FIELD | NVME_DNR;
>> }
>>
>> @@ -4094,7 +4095,6 @@ static uint16_t nvme_smart_info(NvmeCtrl *n, uint8_t
>> rae, uint32_t buf_len,
>> }
>> }
>>
>> - trans_len = MIN(sizeof(smart) - off, buf_len);
>> smart.critical_warning = n->smart_critical_warning;
>>
>> smart.data_units_read[0] = cpu_to_le64(DIV_ROUND_UP(stats.units_read,
>
> Uhm. Hehe.
>
> This "fix" breaks all log pages. Take smart_info as an example. Say the
> offset is zero and the buffer length is 512. The transfer length
> (trans_len) then becomes 512 and it ends up returning Invalid Field in
> Command because trans_len equals sizeof(smart).
>
> Worse, this "fix" actually *introduce* oob's all over the place if
>
> off > sizeof(smart) && buf_len < sizeof(smart)
>
>
> Example
>
> sizeof(smart) = 512
> off = 516 (must be dword aligned to get to this spot)
> buf_len = 4 (same, but is always aligned)
> => trans_len = min(512 - 516, 4) = 4
> if (1 >= 512) => false
>
> And we end up with
>
> nvme_c2h(n, &smart + 516, 4, req);
Doh, I missed the '+ off' part in the nvme_c2h() call...
