linux-kernel - Re: [PATCH] net: core: Fix Spectre v1 vulnerability

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Date:   Sat, 22 Dec 2018 15:07:22 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     gustavo@...eddedor.com
Cc:     ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: core: Fix Spectre v1 vulnerability

From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Date: Fri, 21 Dec 2018 14:49:01 -0600

> flen is 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:
> 
> net/core/filter.c:1101 bpf_check_classic() warn: potential spectre issue 'filter' [w]
> 
> Fix this by sanitizing flen before using it to index filter at line 1101:
> 
> 	switch (filter[flen - 1].code) {
> 
> and through pc at line 1040:
> 	
> 	const struct sock_filter *ftest = &filter[pc];
> 
> 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
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>

BPF folks, I'll take this directly.

Applied and queued up for -stable, thanks.