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    Subject[PATCH 3.13.y-ckt 010/136] arm64: Clear out any singlestep state on a ptrace detach operation
    Date
    3.13.11-ckt34 -stable review patch.  If anyone has any objections, please let me know.

    ---8<------------------------------------------------------------

    From: John Blackwood <john.blackwood@ccur.com>

    commit 5db4fd8c52810bd9740c1240ebf89223b171aa70 upstream.

    Make sure to clear out any ptrace singlestep state when a ptrace(2)
    PTRACE_DETACH call is made on arm64 systems.

    Otherwise, the previously ptraced task will die off with a SIGTRAP
    signal if the debugger just previously singlestepped the ptraced task.

    Signed-off-by: John Blackwood <john.blackwood@ccur.com>
    [will: added comment to justify why this is in the arch code]
    Signed-off-by: Will Deacon <will.deacon@arm.com>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    arch/arm64/kernel/ptrace.c | 6 ++++++
    1 file changed, 6 insertions(+)

    diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
    index b1269da..bfe4a42 100644
    --- a/arch/arm64/kernel/ptrace.c
    +++ b/arch/arm64/kernel/ptrace.c
    @@ -51,6 +51,12 @@
    */
    void ptrace_disable(struct task_struct *child)
    {
    + /*
    + * This would be better off in core code, but PTRACE_DETACH has
    + * grown its fair share of arch-specific worts and changing it
    + * is likely to cause regressions on obscure architectures.
    + */
    + user_disable_single_step(child);
    }

    #ifdef CONFIG_HAVE_HW_BREAKPOINT
    --
    1.9.1
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