Re: [PATCH] ptp: fix Spectre v1 vulnerability

[David Miller <davem@davemloft.net>]

From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Tue, 16 Oct 2018 15:06:41 +0200

> pin_index can be indirectly controlled by user-space, hence leading
> to a potential exploitation of the Spectre variant 1 vulnerability.
> 
> This issue was detected with the help of Smatch:
> 
> drivers/ptp/ptp_chardev.c:253 ptp_ioctl() warn: potential spectre issue
> 'ops->pin_config' [r] (local cap)
> 
> Fix this by sanitizing pin_index before using it to index
> ops->pin_config, and before passing it as an argument to
> function ptp_set_pinfunc(), in which it is used to index
> info->pin_config.
> 
> Notice that given that speculation windows are large, the policy is
> to kill the speculation on the first load and not worry if it can be
> completed with a dependent load/store [1].
> 
> [1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

Applied.