linux-kernel - [PATCH 4.19 028/361] kprobes/x86: Use preempt_enable() in optimized

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Message-Id: <20181111221623.591191775@linuxfoundation.org>
Date:   Sun, 11 Nov 2018 14:16:15 -0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nadav Amit <namit@...are.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>, dwmw@...zon.co.uk,
        Ingo Molnar <mingo@...nel.org>
Subject: [PATCH 4.19 028/361] kprobes/x86: Use preempt_enable() in optimized_callback()

4.19-stable review patch.  If anyone has any objections, please let me know.

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

From: Masami Hiramatsu <mhiramat@...nel.org>

commit 2e62024c265aa69315ed02835623740030435380 upstream.

The following commit:

  a19b2e3d7839 ("kprobes/x86: Remove IRQ disabling from ftrace-based/optimized kprobes”)

removed local_irq_save/restore() from optimized_callback(), the handler
might be interrupted by the rescheduling interrupt and might be
rescheduled - so we must not use the preempt_enable_no_resched() macro.

Use preempt_enable() instead, to not lose preemption events.

[ mingo: Improved the changelog. ]

Reported-by: Nadav Amit <namit@...are.com>
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: <stable@...r.kernel.org>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: dwmw@...zon.co.uk
Fixes: a19b2e3d7839 ("kprobes/x86: Remove IRQ disabling from ftrace-based/optimized kprobes”)
Link: http://lkml.kernel.org/r/154002887331.7627.10194920925792947001.stgit@devbox
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kernel/kprobes/opt.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -179,7 +179,7 @@ optimized_callback(struct optimized_kpro
 		opt_pre_handler(&op->kp, regs);
 		__this_cpu_write(current_kprobe, NULL);
 	}
-	preempt_enable_no_resched();
+	preempt_enable();
 }
 NOKPROBE_SYMBOL(optimized_callback);