Commit 014940ba authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

uprobes/x86: Send SIGILL if arch_uprobe_post_xol() fails 



Currently the error from arch_uprobe_post_xol() is silently ignored.
This doesn't look good and this can lead to the hard-to-debug problems.

1. Change handle_singlestep() to loudly complain and send SIGILL.

   Note: this only affects x86, ppc/arm can't fail.

2. Change arch_uprobe_post_xol() to call arch_uprobe_abort_xol() and
   avoid TF games if it is going to return an error.

   This can help to to analyze the problem, if nothing else we should
   not report ->ip = xol_slot in the core-file.

   Note: this means that handle_riprel_post_xol() can be called twice,
   but this is fine because it is idempotent.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Reviewed-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Reviewed-by: default avatarJim Keniston <jkenisto@us.ibm.com>
parent e55848a4

arch/x86/kernel/uprobes.c

+12 −4
Original line number Diff line number Diff line
@@ -594,6 +594,15 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) 
	struct uprobe_task *utask = current->utask;



	WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR);



	if (auprobe->ops->post_xol) {

		int err = auprobe->ops->post_xol(auprobe, regs);

		if (err) {

			arch_uprobe_abort_xol(auprobe, regs);

			return err;

		}

	}



	current->thread.trap_nr = utask->autask.saved_trap_nr;

	/*

	 * arch_uprobe_pre_xol() doesn't save the state of TIF_BLOCKSTEP
@@ -605,8 +614,6 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) 
	else if (!(auprobe->fixups & UPROBE_FIX_SETF))

		regs->flags &= ~X86_EFLAGS_TF;



	if (auprobe->ops->post_xol)

		return auprobe->ops->post_xol(auprobe, regs);

	return 0;

}
@@ -641,8 +648,9 @@ int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, 


/*

 * This function gets called when XOL instruction either gets trapped or

 * the thread has a fatal signal, so reset the instruction pointer to its

 * probed address.

 * the thread has a fatal signal, or if arch_uprobe_post_xol() failed.

 * Reset the instruction pointer to its probed address for the potential

 * restart or for post mortem analysis.

 */

void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)

{

kernel/events/uprobes.c

+7 −1
Original line number Diff line number Diff line
@@ -1867,10 +1867,11 @@ out: 
static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs)

{

	struct uprobe *uprobe;

	int err = 0;



	uprobe = utask->active_uprobe;

	if (utask->state == UTASK_SSTEP_ACK)

		arch_uprobe_post_xol(&uprobe->arch, regs);

		err = arch_uprobe_post_xol(&uprobe->arch, regs);

	else if (utask->state == UTASK_SSTEP_TRAPPED)

		arch_uprobe_abort_xol(&uprobe->arch, regs);

	else
@@ -1884,6 +1885,11 @@ static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs) 
	spin_lock_irq(&current->sighand->siglock);

	recalc_sigpending(); /* see uprobe_deny_signal() */

	spin_unlock_irq(&current->sighand->siglock);



	if (unlikely(err)) {

		uprobe_warn(current, "execute the probed insn, sending SIGILL.");

		force_sig_info(SIGILL, SEND_SIG_FORCED, current);

	}

}



/*

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