[PATCH AUTOSEL 4.18 15/56] bpf, sockmap: fix sock hash count in alloc_sock_hash_elem

[Sasha Levin <Alexander.Levin@microsoft.com>]

From: Daniel Borkmann <daniel@iogearbox.net>

[ 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@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.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 dd87d930f036..e7f65afc4e24 100644
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -2272,8 +2272,10 @@ static struct htab_elem *alloc_sock_hash_elem(struct bpf_htab *htab,
 	}
 	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;
-- 
2.17.1