From: Eric Dumazet <edumazet@google.com> stable inclusion from stable-5.10.65 commit 8692f0bb29927d13a871b198adff1d336a8d2d00 bugzilla: 182361 https://gitee.com/openeuler/kernel/issues/I4EH3U Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit a00df2caffed3883c341d5685f830434312e4a43 ] Even after commit 4785305c05b2 ("ipv6: use siphash in rt6_exception_hash()"), an attacker can still use brute force to learn some secrets from a victim linux host. One way to defeat these attacks is to make the max depth of the hash table bucket a random value. Before this patch, each bucket of the hash table used to store exceptions could contain 6 items under attack. After the patch, each bucket would contains a random number of items, between 6 and 10. The attacker can no longer infer secrets. This is slightly increasing memory size used by the hash table, we do not expect this to be a problem. Following patch is dealing with the same issue in IPv4. Fixes: 35732d01fe31 ("ipv6: introduce a hash table to store dst cache") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Keyu Man <kman001@ucr.edu> Cc: Wei Wang <weiwan@google.com> Cc: Martin KaFai Lau <kafai@fb.com> Reviewed-by: David Ahern <dsahern@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Chen Jun <chenjun102@huawei.com> Acked-by: Weilong Chen <chenweilong@huawei.com> Signed-off-by: Chen Jun <chenjun102@huawei.com> --- net/ipv6/route.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index bcf4fae83a9b..168a7b4d957a 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -1655,6 +1655,7 @@ static int rt6_insert_exception(struct rt6_info *nrt, struct in6_addr *src_key = NULL; struct rt6_exception *rt6_ex; struct fib6_nh *nh = res->nh; + int max_depth; int err = 0; spin_lock_bh(&rt6_exception_lock); @@ -1709,7 +1710,9 @@ static int rt6_insert_exception(struct rt6_info *nrt, bucket->depth++; net->ipv6.rt6_stats->fib_rt_cache++; - if (bucket->depth > FIB6_MAX_DEPTH) + /* Randomize max depth to avoid some side channels attacks. */ + max_depth = FIB6_MAX_DEPTH + prandom_u32_max(FIB6_MAX_DEPTH); + while (bucket->depth > max_depth) rt6_exception_remove_oldest(bucket); out: -- 2.20.1