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    Subject[PATCH v7 04/11] task_isolation: provide strict mode configurable signal
    Date
    Allow userspace to override the default SIGKILL delivered
    when a task_isolation process in STRICT mode does a syscall
    or otherwise synchronously enters the kernel.

    In addition to being able to set the signal, we now also
    pass whether or not the interruption was from a syscall in
    the si_code field of the siginfo.

    Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
    ---
    include/uapi/linux/prctl.h | 2 ++
    kernel/isolation.c | 17 +++++++++++++----
    2 files changed, 15 insertions(+), 4 deletions(-)

    diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
    index 2b8038b0d1e1..a5582ace987f 100644
    --- a/include/uapi/linux/prctl.h
    +++ b/include/uapi/linux/prctl.h
    @@ -202,5 +202,7 @@ struct prctl_mm_map {
    #define PR_GET_TASK_ISOLATION 49
    # define PR_TASK_ISOLATION_ENABLE (1 << 0)
    # define PR_TASK_ISOLATION_STRICT (1 << 1)
    +# define PR_TASK_ISOLATION_SET_SIG(sig) (((sig) & 0x7f) << 8)
    +# define PR_TASK_ISOLATION_GET_SIG(bits) (((bits) >> 8) & 0x7f)

    #endif /* _LINUX_PRCTL_H */
    diff --git a/kernel/isolation.c b/kernel/isolation.c
    index 3779ba670472..44bafcd08bca 100644
    --- a/kernel/isolation.c
    +++ b/kernel/isolation.c
    @@ -77,14 +77,23 @@ void task_isolation_enter(void)
    }
    }

    -static void kill_task_isolation_strict_task(void)
    +static void kill_task_isolation_strict_task(int is_syscall)
    {
    + siginfo_t info = {};
    + int sig;
    +
    /* RCU should have been enabled prior to this point. */
    RCU_LOCKDEP_WARN(!rcu_is_watching(), "kernel entry without RCU");

    dump_stack();
    current->task_isolation_flags &= ~PR_TASK_ISOLATION_ENABLE;
    - send_sig(SIGKILL, current, 1);
    +
    + sig = PR_TASK_ISOLATION_GET_SIG(current->task_isolation_flags);
    + if (sig == 0)
    + sig = SIGKILL;
    + info.si_signo = sig;
    + info.si_code = is_syscall;
    + send_sig_info(sig, &info, current);
    }

    /*
    @@ -103,7 +112,7 @@ void task_isolation_syscall(int syscall)

    pr_warn("%s/%d: task_isolation strict mode violated by syscall %d\n",
    current->comm, current->pid, syscall);
    - kill_task_isolation_strict_task();
    + kill_task_isolation_strict_task(1);
    }

    /*
    @@ -114,5 +123,5 @@ void task_isolation_exception(void)
    {
    pr_warn("%s/%d: task_isolation strict mode violated by exception\n",
    current->comm, current->pid);
    - kill_task_isolation_strict_task();
    + kill_task_isolation_strict_task(0);
    }
    --
    2.1.2


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