linux-kernel - Re: [PATCHv4 bpf-next 2/6] uprobe: Do not emulate/sstep original instruction when ip is changed

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAADnVQJ6CFD6D9gDb5R=ZnAiXVVJxMe+V3Mv+qniwD13-28MTQ@mail.gmail.com>
Date: Wed, 24 Sep 2025 11:47:42 +0200
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Andrii Nakryiko <andrii.nakryiko@...il.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ingo Molnar <mingo@...nel.org>, Oleg Nesterov <oleg@...hat.com>, 
	Masami Hiramatsu <mhiramat@...nel.org>, Andrii Nakryiko <andrii@...nel.org>, bpf <bpf@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, 
	linux-trace-kernel <linux-trace-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>, 
	Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, 
	John Fastabend <john.fastabend@...il.com>, Hao Luo <haoluo@...gle.com>, 
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCHv4 bpf-next 2/6] uprobe: Do not emulate/sstep original
 instruction when ip is changed

On Wed, Sep 24, 2025 at 11:15 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Tue, Sep 16, 2025 at 03:28:52PM -0700, Andrii Nakryiko wrote:
> > On Tue, Sep 16, 2025 at 2:53 PM Jiri Olsa <jolsa@...nel.org> wrote:
> > >
> > > If uprobe handler changes instruction pointer we still execute single
> > > step) or emulate the original instruction and increment the (new) ip
> > > with its length.
> > >
> > > This makes the new instruction pointer bogus and application will
> > > likely crash on illegal instruction execution.
> > >
> > > If user decided to take execution elsewhere, it makes little sense
> > > to execute the original instruction, so let's skip it.
> > >
> > > Acked-by: Oleg Nesterov <oleg@...hat.com>
> > > Acked-by: Andrii Nakryiko <andrii@...nel.org>
> > > Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> > > ---
> > >  kernel/events/uprobes.c | 7 +++++++
> > >  1 file changed, 7 insertions(+)
> > >
> > > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> > > index 7ca1940607bd..2b32c32bcb77 100644
> > > --- a/kernel/events/uprobes.c
> > > +++ b/kernel/events/uprobes.c
> > > @@ -2741,6 +2741,13 @@ static void handle_swbp(struct pt_regs *regs)
> > >
> > >         handler_chain(uprobe, regs);
> > >
> > > +       /*
> > > +        * If user decided to take execution elsewhere, it makes little sense
> > > +        * to execute the original instruction, so let's skip it.
> > > +        */
> > > +       if (instruction_pointer(regs) != bp_vaddr)
> > > +               goto out;
> > > +
> >
> > Peter, Ingo,
> >
> > Are you guys ok with us routing this through the bpf-next tree? We'll
> > have a tiny conflict because in perf/core branch there is
> > arch_uprobe_optimize() call added after handler_chain(), so git merge
> > will be a bit confused, probably. But it should be trivially
> > resolvable.
>
> Nah, I suppose that'll be fine. Thanks!

Thanks! Applied.

Jiri,
in the future, please keep the whole history in the cover letter.
v1->v2, v2->v3. Just v4 changes are nice, but pls copy paste
previous cover letters and expand them.
Also please always include links to previous versions in the cover.
Search on lore sucks. Links in the cover are a much better
way to preserve the history.