Messages in this thread Patch in this message | | | Date | Fri, 21 Dec 2018 14:49:01 -0600 | From | "Gustavo A. R. Silva" <> | Subject | [PATCH] net: core: Fix Spectre v1 vulnerability |
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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@embeddedor.com> --- net/core/filter.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/net/core/filter.c b/net/core/filter.c index 447dd1bad31f..8ec4337256ed 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -73,6 +73,7 @@ #include <linux/seg6_local.h> #include <net/seg6.h> #include <net/seg6_local.h> +#include <linux/nospec.h> /** * sk_filter_trim_cap - run a packet through a socket filter @@ -1035,6 +1036,7 @@ static int bpf_check_classic(const struct sock_filter *filter, bool anc_found; int pc; + flen = array_index_nospec(flen, BPF_MAXINSNS + 1); /* Check the filter code now */ for (pc = 0; pc < flen; pc++) { const struct sock_filter *ftest = &filter[pc]; -- 2.20.1
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