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 > -- Masami Hiramatsu <mhira...@kernel.org>