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    Subject[PATCH 4.19 243/321] bpf: drop refcount if bpf_map_new_fd() fails in map_create()
    Date
    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


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