[PATCH AUTOSEL 4.19 199/219] bpf: drop refcount if bpf_map_new_fd() fails in map_create()

Sasha Levin
2019-11-22T05:55:01Z

From: Peng Sun <sironhide0null@gmail.com>

[ 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 <sironhide0null@gmail.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 90bb0c05c10e9..596959288eb9e 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -559,12 +559,12 @@ static int map_create(union bpf_attr *attr)
err = bpf_map_new_fd(map, f_flags);
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