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    Subject[PATCH 5.10 116/663] bpf: Fix an unitialized value in bpf_iter
    Date
    From: Yonghong Song <yhs@fb.com>

    [ Upstream commit 17d8beda277a36203585943e70c7909b60775fd5 ]

    Commit 15d83c4d7cef ("bpf: Allow loading of a bpf_iter program")
    cached btf_id in struct bpf_iter_target_info so later on
    if it can be checked cheaply compared to checking registered names.

    syzbot found a bug that uninitialized value may occur to
    bpf_iter_target_info->btf_id. This is because we allocated
    bpf_iter_target_info structure with kmalloc and never initialized
    field btf_id afterwards. This uninitialized btf_id is typically
    compared to a u32 bpf program func proto btf_id, and the chance
    of being equal is extremely slim.

    This patch fixed the issue by using kzalloc which will also
    prevent future likely instances due to adding new fields.

    Fixes: 15d83c4d7cef ("bpf: Allow loading of a bpf_iter program")
    Reported-by: syzbot+580f4f2a272e452d55cb@syzkaller.appspotmail.com
    Signed-off-by: Yonghong Song <yhs@fb.com>
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>
    Link: https://lore.kernel.org/bpf/20210212005926.2875002-1-yhs@fb.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    kernel/bpf/bpf_iter.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c
    index 8f10e30ea0b08..e8957e911de31 100644
    --- a/kernel/bpf/bpf_iter.c
    +++ b/kernel/bpf/bpf_iter.c
    @@ -273,7 +273,7 @@ int bpf_iter_reg_target(const struct bpf_iter_reg *reg_info)
    {
    struct bpf_iter_target_info *tinfo;

    - tinfo = kmalloc(sizeof(*tinfo), GFP_KERNEL);
    + tinfo = kzalloc(sizeof(*tinfo), GFP_KERNEL);
    if (!tinfo)
    return -ENOMEM;

    --
    2.27.0


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