From: Daniel Borkmann <daniel@iogearbox.net>
Date: Tue, 21 Aug 2018 15:55:00 +0200
Subject: bpf, sockmap: fix sock_hash_alloc and reject zero-sized keys
Patch-mainline: v4.19-rc2
Git-commit: b845c898b2f1ea458d5453f0fa1da6e2dfce3bb4
References: bsc#1109837

Currently, it is possible to create a sock hash map with key size
of 0 and have the kernel return a fd back to user space. This is
invalid for hash maps (and kernel also hasn't been tested for zero
key size support in general at this point). Thus, reject such
configuration.

Fixes: 81110384441a ("bpf: sockmap, add hash map support")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 kernel/bpf/sockmap.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -2122,7 +2122,9 @@ static struct bpf_map *sock_hash_alloc(u
 		return ERR_PTR(-EPERM);
 
 	/* check sanity of attributes */
-	if (attr->max_entries == 0 || attr->value_size != 4 ||
+	if (attr->max_entries == 0 ||
+	    attr->key_size == 0 ||
+	    attr->value_size != 4 ||
 	    attr->map_flags & ~SOCK_CREATE_FLAG_MASK)
 		return ERR_PTR(-EINVAL);