From f9845426f4427eb0031b562dfd5c0ffe99cba644 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 5 Oct 2017 02:50:07 -0700 Subject: [PATCH] netfilter: x_tables: avoid stack-out-of-bounds read in xt_copy_counters_from_user commit e466af75c074e76107ae1cd5a2823e9c61894ffb upstream. syzkaller reports an out of bound read in strlcpy(), triggered by xt_copy_counters_from_user() Fix this by using memcpy(), then forcing a zero byte at the last position of the destination, as Florian did for the non COMPAT code. Fixes: d7591f0c41ce ("netfilter: x_tables: introduce and use xt_copy_counters_from_user") Signed-off-by: Eric Dumazet Cc: Willem de Bruijn Acked-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso Cc: Greg Hackmann Signed-off-by: Greg Kroah-Hartman --- net/netfilter/x_tables.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c index 1f3c305df45d..b6e72af15237 100644 --- a/net/netfilter/x_tables.c +++ b/net/netfilter/x_tables.c @@ -876,7 +876,7 @@ void *xt_copy_counters_from_user(const void __user *user, unsigned int len, if (copy_from_user(&compat_tmp, user, sizeof(compat_tmp)) != 0) return ERR_PTR(-EFAULT); - strlcpy(info->name, compat_tmp.name, sizeof(info->name)); + memcpy(info->name, compat_tmp.name, sizeof(info->name) - 1); info->num_counters = compat_tmp.num_counters; user += sizeof(compat_tmp); } else @@ -889,9 +889,9 @@ void *xt_copy_counters_from_user(const void __user *user, unsigned int len, if (copy_from_user(info, user, sizeof(*info)) != 0) return ERR_PTR(-EFAULT); - info->name[sizeof(info->name) - 1] = '\0'; user += sizeof(*info); } + info->name[sizeof(info->name) - 1] = '\0'; size = sizeof(struct xt_counters); size *= info->num_counters;