[PATCH 4.18 183/228] bpf, sockmap: fix sock hash count in alloc_sock_hash_elem

[Greg Kroah-Hartman]

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel Borkmann <daniel@xxxxxxxxxxxxx>

[ Upstream commit eb29429d81e31b191f3b2bd19cf820279cec6463 ]

When we try to allocate a new sock hash entry and the allocation
fails, then sock hash map fails to reduce the map element counter,
meaning we keep accounting this element although it was never used.
Fix it by dropping the element counter on error.

Fixes: 81110384441a ("bpf: sockmap, add hash map support")
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 kernel/bpf/sockmap.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -2272,8 +2272,10 @@ static struct htab_elem *alloc_sock_hash
 	}
 	l_new = kmalloc_node(htab->elem_size, GFP_ATOMIC | __GFP_NOWARN,
 			     htab->map.numa_node);
-	if (!l_new)
+	if (!l_new) {
+		atomic_dec(&htab->count);
 		return ERR_PTR(-ENOMEM);
+	}
 
 	memcpy(l_new->key, key, key_size);
 	l_new->sk = sk;