diff mbox series

[4.9.y] arm: kprobes: Allow to handle reentered kprobe on single-stepping

Message ID 20210303071052.33740-1-huangshaobo6@huawei.com (mailing list archive)
State New, archived
Headers show
Series [4.9.y] arm: kprobes: Allow to handle reentered kprobe on single-stepping | expand

Commit Message

ShaoBo Huang March 3, 2021, 7:10 a.m. UTC
From: Masami Hiramatsu <mhiramat@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 <mhiramat@kernel.org>
Signed-off-by: Jon Medhurst <tixy@linaro.org>
Fixes: 24ba613c9d6c ("ARM kprobes: core code")
Cc: stable@vger.kernel.org #v2.6.25~v4.11
Signed-off-by: huangshaobo <huangshaobo6@huawei.com>
---
 arch/arm/probes/kprobes/core.c | 6 ++++++
 1 file changed, 6 insertions(+)

Comments

Greg Kroah-Hartman March 4, 2021, 1:28 p.m. UTC | #1
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 <huangshaobo6@huawei.com> wrote:
> 
> > From: Masami Hiramatsu <mhiramat@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 <mhiramat@kernel.org>
> > Signed-off-by: Jon Medhurst <tixy@linaro.org>
> > Fixes: 24ba613c9d6c ("ARM kprobes: core code")
> > Cc: stable@vger.kernel.org #v2.6.25~v4.11
> > Signed-off-by: huangshaobo <huangshaobo6@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
diff mbox series

Patch

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();