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    Subject[PATCH 5.14 397/849] kprobes: Do not use local variable when creating debugfs file
    Date
    From: Punit Agrawal <punitagrawal@gmail.com>

    [ Upstream commit 8f7262cd66699a4b02eb7549b35c81b2116aad95 ]

    debugfs_create_file() takes a pointer argument that can be used during
    file operation callbacks (accessible via i_private in the inode
    structure). An obvious requirement is for the pointer to refer to
    valid memory when used.

    When creating the debugfs file to dynamically enable / disable
    kprobes, a pointer to local variable is passed to
    debugfs_create_file(); which will go out of scope when the init
    function returns. The reason this hasn't triggered random memory
    corruption is because the pointer is not accessed during the debugfs
    file callbacks.

    Since the enabled state is managed by the kprobes_all_disabled global
    variable, the local variable is not needed. Fix the incorrect (and
    unnecessary) usage of local variable during debugfs_file_create() by
    passing NULL instead.

    Link: https://lkml.kernel.org/r/163163031686.489837.4476867635937014973.stgit@devnote2

    Fixes: bf8f6e5b3e51 ("Kprobes: The ON/OFF knob thru debugfs")
    Signed-off-by: Punit Agrawal <punitagrawal@gmail.com>
    Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
    Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
    Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    kernel/kprobes.c | 3 +--
    1 file changed, 1 insertion(+), 2 deletions(-)

    diff --git a/kernel/kprobes.c b/kernel/kprobes.c
    index 790a573bbe00c..1cf8bca1ea861 100644
    --- a/kernel/kprobes.c
    +++ b/kernel/kprobes.c
    @@ -2809,13 +2809,12 @@ static const struct file_operations fops_kp = {
    static int __init debugfs_kprobe_init(void)
    {
    struct dentry *dir;
    - unsigned int value = 1;

    dir = debugfs_create_dir("kprobes", NULL);

    debugfs_create_file("list", 0400, dir, NULL, &kprobes_fops);

    - debugfs_create_file("enabled", 0600, dir, &value, &fops_kp);
    + debugfs_create_file("enabled", 0600, dir, NULL, &fops_kp);

    debugfs_create_file("blacklist", 0400, dir, NULL,
    &kprobe_blacklist_fops);
    --
    2.33.0


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