[PATCH 4.17 178/324] bpf: hash map: decrement counter on error

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

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

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

From: Mauricio Vasquez B <mauricio.vasquez@xxxxxxxxx>

[ Upstream commit ed2b82c03dc187018307c7c6bf9299705f3db383 ]

Decrement the number of elements in the map in case the allocation
of a new node fails.

Fixes: 6c9059817432 ("bpf: pre-allocate hash map elements")
Signed-off-by: Mauricio Vasquez B <mauricio.vasquez@xxxxxxxxx>
Acked-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 kernel/bpf/hashtab.c |   16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -743,13 +743,15 @@ static struct htab_elem *alloc_htab_elem
 				 * old element will be freed immediately.
 				 * Otherwise return an error
 				 */
-				atomic_dec(&htab->count);
-				return ERR_PTR(-E2BIG);
+				l_new = ERR_PTR(-E2BIG);
+				goto dec_count;
 			}
 		l_new = kmalloc_node(htab->elem_size, GFP_ATOMIC | __GFP_NOWARN,
 				     htab->map.numa_node);
-		if (!l_new)
-			return ERR_PTR(-ENOMEM);
+		if (!l_new) {
+			l_new = ERR_PTR(-ENOMEM);
+			goto dec_count;
+		}
 	}
 
 	memcpy(l_new->key, key, key_size);
@@ -762,7 +764,8 @@ static struct htab_elem *alloc_htab_elem
 						  GFP_ATOMIC | __GFP_NOWARN);
 			if (!pptr) {
 				kfree(l_new);
-				return ERR_PTR(-ENOMEM);
+				l_new = ERR_PTR(-ENOMEM);
+				goto dec_count;
 			}
 		}
 
@@ -776,6 +779,9 @@ static struct htab_elem *alloc_htab_elem
 
 	l_new->hash = hash;
 	return l_new;
+dec_count:
+	atomic_dec(&htab->count);
+	return l_new;
 }
 
 static int check_flags(struct bpf_htab *htab, struct htab_elem *l_old,