netfilter: x_tables: avoid stack-out-of-bounds read in xt_copy_counters_from_user (e466af75) · Commits · 戴 / test

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: ("netfilter: x_tables: introduce and use xt_copy_counters_from_user") Signed-off-by:

Eric Dumazet <edumazet@google.com> Cc: Willem de Bruijn <willemb@google.com> Acked-by:

Florian Westphal <fw@strlen.de> Signed-off-by:

Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/x_tables.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -892,7 +892,7 @@ 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
		@@ -905,9 +905,9 @@ 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;

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