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    Subject[PATCH 4.19 016/131] apparmor: don't try to replace stale label in ptraceme check
    Date
    From: Jann Horn <jannh@google.com>

    [ Upstream commit ca3fde5214e1d24f78269b337d3f22afd6bf445e ]

    begin_current_label_crit_section() must run in sleepable context because
    when label_is_stale() is true, aa_replace_current_label() runs, which uses
    prepare_creds(), which can sleep.

    Until now, the ptraceme access check (which runs with tasklist_lock held)
    violated this rule.

    Fixes: b2d09ae449ced ("apparmor: move ptrace checks to using labels")
    Reported-by: Cyrill Gorcunov <gorcunov@gmail.com>
    Reported-by: kernel test robot <rong.a.chen@intel.com>
    Signed-off-by: Jann Horn <jannh@google.com>
    Signed-off-by: John Johansen <john.johansen@canonical.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    security/apparmor/lsm.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
    index 5e32fe434140e..898752b818dc5 100644
    --- a/security/apparmor/lsm.c
    +++ b/security/apparmor/lsm.c
    @@ -130,11 +130,11 @@ static int apparmor_ptrace_traceme(struct task_struct *parent)
    struct aa_label *tracer, *tracee;
    int error;

    - tracee = begin_current_label_crit_section();
    + tracee = __begin_current_label_crit_section();
    tracer = aa_get_task_label(parent);
    error = aa_may_ptrace(tracer, tracee, AA_PTRACE_TRACE);
    aa_put_label(tracer);
    - end_current_label_crit_section(tracee);
    + __end_current_label_crit_section(tracee);

    return error;
    }
    --
    2.25.1
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