[PATCH AUTOSEL 4.18 14/56] bpf, sockmap: fix sock_hash_alloc and reject zero-sized keys

[Sasha Levin]

From: Daniel Borkmann <daniel@xxxxxxxxxxxxx>

[ Upstream commit b845c898b2f1ea458d5453f0fa1da6e2dfce3bb4 ]

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@xxxxxxxxxxxxx>
Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
Acked-by: Song Liu <songliubraving@xxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
---
 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 58899601fccf..dd87d930f036 100644
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -2143,7 +2143,9 @@ 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);
 
-- 
2.17.1