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    Subject[PATCH 3.17 018/122] uprobes, x86: Fix _TIF_UPROBE vs _TIF_NOTIFY_RESUME
    Date
    3.17-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Andy Lutomirski <luto@amacapital.net>

    commit 82975bc6a6df743b9a01810fb32cb65d0ec5d60b upstream.

    x86 call do_notify_resume on paranoid returns if TIF_UPROBE is set but
    not on non-paranoid returns. I suspect that this is a mistake and that
    the code only works because int3 is paranoid.

    Setting _TIF_NOTIFY_RESUME in the uprobe code was probably a workaround
    for the x86 bug. With that bug fixed, we can remove _TIF_NOTIFY_RESUME
    from the uprobes code.

    Reported-by: Oleg Nesterov <oleg@redhat.com>
    Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
    Acked-by: Borislav Petkov <bp@suse.de>
    Signed-off-by: Andy Lutomirski <luto@amacapital.net>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/include/asm/thread_info.h | 2 +-
    kernel/events/uprobes.c | 1 -
    2 files changed, 1 insertion(+), 2 deletions(-)

    --- a/arch/x86/include/asm/thread_info.h
    +++ b/arch/x86/include/asm/thread_info.h
    @@ -141,7 +141,7 @@ struct thread_info {
    /* Only used for 64 bit */
    #define _TIF_DO_NOTIFY_MASK \
    (_TIF_SIGPENDING | _TIF_MCE_NOTIFY | _TIF_NOTIFY_RESUME | \
    - _TIF_USER_RETURN_NOTIFY)
    + _TIF_USER_RETURN_NOTIFY | _TIF_UPROBE)

    /* flags to check in __switch_to() */
    #define _TIF_WORK_CTXSW \
    --- a/kernel/events/uprobes.c
    +++ b/kernel/events/uprobes.c
    @@ -1640,7 +1640,6 @@ bool uprobe_deny_signal(void)
    if (__fatal_signal_pending(t) || arch_uprobe_xol_was_trapped(t)) {
    utask->state = UTASK_SSTEP_TRAPPED;
    set_tsk_thread_flag(t, TIF_UPROBE);
    - set_tsk_thread_flag(t, TIF_NOTIFY_RESUME);
    }
    }




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