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@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Song Liu <songliubraving@fb.com>

diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
index 98e621a29e8e6953ec9dec5b4cb6f8559dd750d3..60ceb0e1fa56b017fc3ee8b5720caf65c301f09f 100644 (file)
--- 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);