Re: [PATCH 2/2] kprobes/x86: Check for invalid ftrace location in __recover_probed_insn()
From: Ingo Molnar
Date: Fri Feb 20 2015 - 05:19:35 EST
* Petr Mladek <pmladek@xxxxxxx> wrote:
> __recover_probed_insn() should always be called from an address where
> an instructions starts. The check for ftrace_location() might help to
> discover a potential inconsistency. Something goes terribly wrong when
> an address inside the ftrace location is checked. Let's BUG() in this case.
> Suggested-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
> Signed-off-by: Petr Mladek <pmladek@xxxxxxx>
> Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
> arch/x86/kernel/kprobes/core.c | 6 ++++++
> 1 file changed, 6 insertions(+)
> diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
> index 2f464b56766a..124577dcf768 100644
> --- a/arch/x86/kernel/kprobes/core.c
> +++ b/arch/x86/kernel/kprobes/core.c
> @@ -228,6 +228,12 @@ __recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr)
> kp = get_kprobe((void *)addr);
> faddr = ftrace_location(addr);
> + * Addresses inside the ftrace location are refused by
> + * arch_check_ftrace_location(). Something went terribly wrong
> + * if such an address is checked here.
> + */
> + BUG_ON(faddr && faddr != addr);
Crashing the system with a BUG_ON() makes users very sad.
Please use a construct like:
if (WARN_ON(faddr && faddr != addr))
I've picked up your first patch.
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