netdev - [PATCH bpf] bpf, sockmap: fix sock_hash_alloc and reject zero-sized keys

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Date:   Wed, 22 Aug 2018 00:02:29 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     alexei.starovoitov@...il.com
Cc:     john.fastabend@...il.com, netdev@...r.kernel.org,
        Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH bpf] bpf, sockmap: fix sock_hash_alloc and reject zero-sized keys

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@...earbox.net>
Acked-by: John Fastabend <john.fastabend@...il.com>
---
 kernel/bpf/sockmap.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
index 98e621a..60ceb0e 100644
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -2140,7 +2140,9 @@ static struct bpf_map *sock_hash_alloc(union bpf_attr *attr)
 		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);
 
-- 
2.9.5