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    Subject[PATCH 5.15 146/846] libbpf: Fix potential misaligned memory access in btf_ext__new()
    Date
    From: Andrii Nakryiko <andrii@kernel.org>

    [ Upstream commit 401891a9debaf0a684502f2aaecf53448cee9414 ]

    Perform a memory copy before we do the sanity checks of btf_ext_hdr.
    This prevents misaligned memory access if raw btf_ext data is not 4-byte
    aligned ([0]).

    While at it, also add missing const qualifier.

    [0] Closes: https://github.com/libbpf/libbpf/issues/391

    Fixes: 2993e0515bb4 ("tools/bpf: add support to read .BTF.ext sections")
    Reported-by: Evgeny Vereshchagin <evvers@ya.ru>
    Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
    Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
    Link: https://lore.kernel.org/bpf/20211124002325.1737739-3-andrii@kernel.org
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    tools/lib/bpf/btf.c | 10 +++++-----
    tools/lib/bpf/btf.h | 2 +-
    2 files changed, 6 insertions(+), 6 deletions(-)

    diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
    index 1b9341ef638b0..5fa64a7f0dda8 100644
    --- a/tools/lib/bpf/btf.c
    +++ b/tools/lib/bpf/btf.c
    @@ -2626,15 +2626,11 @@ void btf_ext__free(struct btf_ext *btf_ext)
    free(btf_ext);
    }

    -struct btf_ext *btf_ext__new(__u8 *data, __u32 size)
    +struct btf_ext *btf_ext__new(const __u8 *data, __u32 size)
    {
    struct btf_ext *btf_ext;
    int err;

    - err = btf_ext_parse_hdr(data, size);
    - if (err)
    - return libbpf_err_ptr(err);
    -
    btf_ext = calloc(1, sizeof(struct btf_ext));
    if (!btf_ext)
    return libbpf_err_ptr(-ENOMEM);
    @@ -2647,6 +2643,10 @@ struct btf_ext *btf_ext__new(__u8 *data, __u32 size)
    }
    memcpy(btf_ext->data, data, size);

    + err = btf_ext_parse_hdr(btf_ext->data, size);
    + if (err)
    + goto done;
    +
    if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, line_info_len)) {
    err = -EINVAL;
    goto done;
    diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
    index 4a711f990904b..b0ee338a0cc87 100644
    --- a/tools/lib/bpf/btf.h
    +++ b/tools/lib/bpf/btf.h
    @@ -80,7 +80,7 @@ LIBBPF_API int btf__get_map_kv_tids(const struct btf *btf, const char *map_name,
    __u32 expected_value_size,
    __u32 *key_type_id, __u32 *value_type_id);

    -LIBBPF_API struct btf_ext *btf_ext__new(__u8 *data, __u32 size);
    +LIBBPF_API struct btf_ext *btf_ext__new(const __u8 *data, __u32 size);
    LIBBPF_API void btf_ext__free(struct btf_ext *btf_ext);
    LIBBPF_API const void *btf_ext__get_raw_data(const struct btf_ext *btf_ext,
    __u32 *size);
    --
    2.34.1


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