Subject: [PATCH AUTOSEL 4.14 117/127] bpf: drop refcount if bpf_map_new_fd() fails in map_create()

From: Sasha Levin <[email-masked]>
Date: Fri, 22 Nov 2019 00:55:34 -0500

From: Peng Sun <[email-masked]>

[ Upstream commit 352d20d611414715353ee65fc206ee57ab1a6984 ]

In bpf/syscall.c, map_create() first set map->usercnt to 1, a file
descriptor is supposed to return to userspace. When bpf_map_new_fd()
fails, drop the refcount.

Fixes: bd5f5f4ecb78 ("bpf: Add BPF_MAP_GET_FD_BY_ID")
Signed-off-by: Peng Sun <[email-masked]>
Acked-by: Martin KaFai Lau <[email-masked]>
Signed-off-by: Alexei Starovoitov <[email-masked]>
Signed-off-by: Daniel Borkmann <[email-masked]>
Signed-off-by: Sasha Levin <[email-masked]>
---
 kernel/bpf/syscall.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 34110450a78f2..f5c1d5479ba3d 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -348,12 +348,12 @@ static int map_create(union bpf_attr *attr)
 	err = bpf_map_new_fd(map);
 	if (err < 0) {
 		/* failed to allocate fd.
-		 * bpf_map_put() is needed because the above
+		 * bpf_map_put_with_uref() is needed because the above
 		 * bpf_map_alloc_id() has published the map
 		 * to the userspace and the userspace may
 		 * have refcnt-ed it through BPF_MAP_GET_FD_BY_ID.
 		 */
-		bpf_map_put(map);
+		bpf_map_put_with_uref(map);
 		return err;
 	}
 
-- 
2.20.1