[PATCH 5.10 139/145] netfilter: xt_RATEEST: reject non-null terminated string from userspace

[Greg Kroah-Hartman]

From: Florian Westphal <f...@strlen.de>

commit 6cb56218ad9e580e519dcd23bfb3db08d8692e5a upstream.

syzbot reports:
detected buffer overflow in strlen
[..]
Call Trace:
 strlen include/linux/string.h:325 [inline]
 strlcpy include/linux/string.h:348 [inline]
 xt_rateest_tg_checkentry+0x2a5/0x6b0 net/netfilter/xt_RATEEST.c:143

strlcpy assumes src is a c-string. Check info->name before its used.

Reported-by: syzbot+e86f7c428c8c50db6...@syzkaller.appspotmail.com
Fixes: 5859034d7eb8793 ("[NETFILTER]: x_tables: add RATEEST target")
Signed-off-by: Florian Westphal <f...@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pa...@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 net/netfilter/xt_RATEEST.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/netfilter/xt_RATEEST.c
+++ b/net/netfilter/xt_RATEEST.c
@@ -115,6 +115,9 @@ static int xt_rateest_tg_checkentry(cons
        } cfg;
        int ret;
 
+       if (strnlen(info->name, sizeof(est->name)) >= sizeof(est->name))
+               return -ENAMETOOLONG;
+
        net_get_random_once(&jhash_rnd, sizeof(jhash_rnd));
 
        mutex_lock(&xn->hash_lock);