This is a note to let you know that I've just added the patch titled
powerpc/kprobes: Disable preemption before invoking probe handler for optprobes
to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: powerpc-kprobes-disable-preemption-before-invoking-probe-handler-for-optprobes.patch and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 8a2d71a3f2737e2448aa68de2b6052cb570d3d2a Mon Sep 17 00:00:00 2001
From: "Naveen N. Rao" naveen.n.rao@linux.vnet.ibm.com Date: Mon, 23 Oct 2017 22:07:38 +0530 Subject: powerpc/kprobes: Disable preemption before invoking probe handler for optprobes
From: Naveen N. Rao naveen.n.rao@linux.vnet.ibm.com
commit 8a2d71a3f2737e2448aa68de2b6052cb570d3d2a upstream.
Per Documentation/kprobes.txt, probe handlers need to be invoked with preemption disabled. Update optimized_callback() to do so. Also move get_kprobe_ctlblk() invocation post preemption disable, since it accesses pre-cpu data.
This was not an issue so far since optprobes wasn't selected if CONFIG_PREEMPT was enabled. Commit a30b85df7d599f ("kprobes: Use synchronize_rcu_tasks() for optprobe with CONFIG_PREEMPT=y") changes this.
Signed-off-by: Naveen N. Rao naveen.n.rao@linux.vnet.ibm.com Acked-by: Masami Hiramatsu mhiramat@kernel.org Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/kernel/optprobes.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/arch/powerpc/kernel/optprobes.c +++ b/arch/powerpc/kernel/optprobes.c @@ -115,7 +115,6 @@ static unsigned long can_optimize(struct static void optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs) { - struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); unsigned long flags;
/* This is possible if op is under delayed unoptimizing */ @@ -124,13 +123,14 @@ static void optimized_callback(struct op
local_irq_save(flags); hard_irq_disable(); + preempt_disable();
if (kprobe_running()) { kprobes_inc_nmissed_count(&op->kp); } else { __this_cpu_write(current_kprobe, &op->kp); regs->nip = (unsigned long)op->kp.addr; - kcb->kprobe_status = KPROBE_HIT_ACTIVE; + get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE; opt_pre_handler(&op->kp, regs); __this_cpu_write(current_kprobe, NULL); } @@ -140,6 +140,7 @@ static void optimized_callback(struct op * local_irq_restore() will re-enable interrupts, * if they were hard disabled. */ + preempt_enable_no_resched(); local_irq_restore(flags); } NOKPROBE_SYMBOL(optimized_callback);
Patches currently in stable-queue which might be from naveen.n.rao@linux.vnet.ibm.com are
queue-4.14/kprobes-use-synchronize_rcu_tasks-for-optprobe-with-config_preempt-y.patch queue-4.14/powerpc-kprobes-disable-preemption-before-invoking-probe-handler-for-optprobes.patch queue-4.14/powerpc-jprobes-disable-preemption-when-triggered-through-ftrace.patch