linux-kernel - [PATCH 4.19 243/321] bpf: drop refcount if bpf_map_new_fd() fails in map

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Message-Id: <20191203223439.782973932@linuxfoundation.org>
Date:   Tue,  3 Dec 2019 23:35:09 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Peng Sun <sironhide0null@...il.com>,
        Martin KaFai Lau <kafai@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 243/321] bpf: drop refcount if bpf_map_new_fd() fails in map_create()

From: Peng Sun <sironhide0null@...il.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@...il.com>
Acked-by: Martin KaFai Lau <kafai@...com>
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Signed-off-by: Sasha Levin <sashal@...nel.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