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    Subject[PATCH 5.1 197/371] bpf, libbpf, smatch: Fix potential NULL pointer dereference
    Date
    [ Upstream commit 33bae185f74d49a0d7b1bfaafb8e959efce0f243 ]

    Based on the following report from Smatch, fix the potential NULL
    pointer dereference check:

    tools/lib/bpf/libbpf.c:3493
    bpf_prog_load_xattr() warn: variable dereferenced before check 'attr'
    (see line 3483)

    3479 int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
    3480 struct bpf_object **pobj, int *prog_fd)
    3481 {
    3482 struct bpf_object_open_attr open_attr = {
    3483 .file = attr->file,
    3484 .prog_type = attr->prog_type,
    ^^^^^^
    3485 };

    At the head of function, it directly access 'attr' without checking
    if it's NULL pointer. This patch moves the values assignment after
    validating 'attr' and 'attr->file'.

    Signed-off-by: Leo Yan <leo.yan@linaro.org>
    Acked-by: Yonghong Song <yhs@fb.com>
    Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    tools/lib/bpf/libbpf.c | 8 ++++----
    1 file changed, 4 insertions(+), 4 deletions(-)

    diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
    index 11c25d9ea431..43dc8a8e9105 100644
    --- a/tools/lib/bpf/libbpf.c
    +++ b/tools/lib/bpf/libbpf.c
    @@ -2897,10 +2897,7 @@ int bpf_prog_load(const char *file, enum bpf_prog_type type,
    int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
    struct bpf_object **pobj, int *prog_fd)
    {
    - struct bpf_object_open_attr open_attr = {
    - .file = attr->file,
    - .prog_type = attr->prog_type,
    - };
    + struct bpf_object_open_attr open_attr = {};
    struct bpf_program *prog, *first_prog = NULL;
    enum bpf_attach_type expected_attach_type;
    enum bpf_prog_type prog_type;
    @@ -2913,6 +2910,9 @@ int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
    if (!attr->file)
    return -EINVAL;

    + open_attr.file = attr->file;
    + open_attr.prog_type = attr->prog_type;
    +
    obj = bpf_object__open_xattr(&open_attr);
    if (IS_ERR_OR_NULL(obj))
    return -ENOENT;
    --
    2.20.1


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