Re: [PATCH-for-6.2 v2 2/2] hw/nvme/ctrl: Prevent buffer overrun in nvme_error_info()

[Klaus Jensen <its@irrelevant.dk>]

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On Nov 17 13:35, 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-stable@nongnu.org
> Fixes: 94a7897c41d ("add support for the get log page command")
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  hw/nvme/ctrl.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
> index 93a24464647..7414f3b4dd1 100644
> --- a/hw/nvme/ctrl.c
> +++ b/hw/nvme/ctrl.c
> @@ -4146,7 +4146,8 @@ static uint16_t nvme_error_info(NvmeCtrl *n, uint8_t rae, uint32_t buf_len,
>      uint32_t trans_len;
>      NvmeErrorLog errlog;
>  
> -    if (off >= sizeof(errlog)) {
> +    trans_len = MIN(sizeof(errlog) - off, buf_len);
> +    if (trans_len >= sizeof(errlog)) {
>          return NVME_INVALID_FIELD | NVME_DNR;
>      }
>  
> @@ -4155,7 +4156,6 @@ static uint16_t nvme_error_info(NvmeCtrl *n, uint8_t rae, uint32_t buf_len,
>      }
>  
>      memset(&errlog, 0x0, sizeof(errlog));
> -    trans_len = MIN(sizeof(errlog) - off, buf_len);
>  
>      return nvme_c2h(n, (uint8_t *)&errlog, trans_len, req);
>  }
> -- 
> 2.31.1
> 

I don't see any buffer overrun issue prior to this patch. However, there
is a functional bug since the offset is not added in the c2h.

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