Commit 50d52586 authored by Gustavo A. R. Silva's avatar Gustavo A. R. Silva Committed by David S. Miller

net: core: Fix Spectre v1 vulnerability

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=2Signed-off-by: default avatarGustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 6cafab50
...@@ -73,6 +73,7 @@ ...@@ -73,6 +73,7 @@
#include <linux/seg6_local.h> #include <linux/seg6_local.h>
#include <net/seg6.h> #include <net/seg6.h>
#include <net/seg6_local.h> #include <net/seg6_local.h>
#include <linux/nospec.h>
/** /**
* sk_filter_trim_cap - run a packet through a socket filter * sk_filter_trim_cap - run a packet through a socket filter
...@@ -1038,6 +1039,7 @@ static int bpf_check_classic(const struct sock_filter *filter, ...@@ -1038,6 +1039,7 @@ static int bpf_check_classic(const struct sock_filter *filter,
bool anc_found; bool anc_found;
int pc; int pc;
flen = array_index_nospec(flen, BPF_MAXINSNS + 1);
/* Check the filter code now */ /* Check the filter code now */
for (pc = 0; pc < flen; pc++) { for (pc = 0; pc < flen; pc++) {
const struct sock_filter *ftest = &filter[pc]; const struct sock_filter *ftest = &filter[pc];
......
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