On Wed, Mar 03, 2021 at 09:18:27PM +0900, Masami Hiramatsu wrote:
> Hi ShaoBo,
>
> Thanks for backporting and real bug report!
>
> On Wed, 3 Mar 2021 15:10:52 +0800
> ShaoBo Huang <huangshao...@huawei.com> wrote:
>
> > From: Masami Hiramatsu <mhira...@kernel.org>
> >
> > commit f3fbd7ec62dec1528fb8044034e2885f2b257941 upstream
> >
> > This is arm port of commit 6a5022a56ac3 ("kprobes/x86: Allow to
> > handle reentered kprobe on single-stepping")
> >
> > Since the FIQ handlers can interrupt in the single stepping
> > (or preparing the single stepping, do_debug etc.), we should
> > consider a kprobe is hit in the NMI handler. Even in that
> > case, the kprobe is allowed to be reentered as same as the
> > kprobes hit in kprobe handlers
> > (KPROBE_HIT_ACTIVE or KPROBE_HIT_SSDONE).
> >
> > The real issue will happen when a kprobe hit while another
> > reentered kprobe is processing (KPROBE_REENTER), because
> > we already consumed a saved-area for the previous kprobe.
> >
> > Signed-off-by: Masami Hiramatsu <mhira...@kernel.org>
> > Signed-off-by: Jon Medhurst <t...@linaro.org>
> > Fixes: 24ba613c9d6c ("ARM kprobes: core code")
> > Cc: sta...@vger.kernel.org #v2.6.25~v4.11
> > Signed-off-by: huangshaobo <huangshao...@huawei.com>
> > ---
> > arch/arm/probes/kprobes/core.c | 6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> > diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c
> > index 3eb018fa1a1f..c3362ddd6c4c 100644
> > --- a/arch/arm/probes/kprobes/core.c
> > +++ b/arch/arm/probes/kprobes/core.c
> > @@ -270,6 +270,7 @@ void __kprobes kprobe_handler(struct pt_regs *regs)
> > switch (kcb->kprobe_status) {
> > case KPROBE_HIT_ACTIVE:
> > case KPROBE_HIT_SSDONE:
> > + case KPROBE_HIT_SS:
> > /* A pre- or post-handler probe got us here. */
> > kprobes_inc_nmissed_count(p);
> > save_previous_kprobe(kcb);
> > @@ -278,6 +279,11 @@ void __kprobes kprobe_handler(struct pt_regs *regs)
> > singlestep(p, regs, kcb);
> > restore_previous_kprobe(kcb);
> > break;
> > + case KPROBE_REENTER:
> > + /* A nested probe was hit in FIQ, it is a BUG */
> > + pr_warn("Unrecoverable kprobe detected at
> > %p.\n",
> > + p->addr);
> > + /* fall through */
> > default:
> > /* impossible cases */
> > BUG();
> > --
> > 2.12.3
> >
Also queued up to 4.4.y as well.
thanks,
greg k-h
