netfilter: x_tables: avoid out-of-bounds reads in xt_request_find_{match|target}

commit da17c73b6eb74aad3c3c0654394635675b623b3e upstream.

It looks like syzbot found its way into netfilter territory.

Issue here is that @name comes from user space and might
not be null terminated.

Out-of-bound reads happen, KASAN is not happy.

v2 added similar fix for xt_request_find_target(),
as Florian advised.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 20f7856..60c9215 100644 (file)
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -209,6 +209,9 @@ xt_request_find_match(uint8_t nfproto, const char *name, uint8_t revision)
 {
        struct xt_match *match;
 
+       if (strnlen(name, XT_EXTENSION_MAXNAMELEN) == XT_EXTENSION_MAXNAMELEN)
+               return ERR_PTR(-EINVAL);
+
        match = xt_find_match(nfproto, name, revision);
        if (IS_ERR(match)) {
                request_module("%st_%s", xt_prefix[nfproto], name);
@@ -251,6 +254,9 @@ struct xt_target *xt_request_find_target(u8 af, const char *name, u8 revision)
 {
        struct xt_target *target;
 
+       if (strnlen(name, XT_EXTENSION_MAXNAMELEN) == XT_EXTENSION_MAXNAMELEN)
+               return ERR_PTR(-EINVAL);
+
        target = xt_find_target(af, name, revision);
        if (IS_ERR(target)) {
                request_module("%st_%s", xt_prefix[af], name);