linux-kernel - Re: [PATCHv2 perf/core] uprobes: Harden uretprobe syscall trampoline check

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Message-Id: <20250212130509.ce1987095c6b17b26d3ee40a@kernel.org>
Date: Wed, 12 Feb 2025 13:05:09 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>, Andrii Nakryiko
 <andrii.nakryiko@...il.com>, Jiri Olsa <jolsa@...nel.org>, Steven Rostedt
 <rostedt@...dmis.org>, Masami Hiramatsu <mhiramat@...nel.org>, Peter
 Zijlstra <peterz@...radead.org>, Andrii Nakryiko <andrii@...nel.org>, Kees
 Cook <kees@...nel.org>, Eyal Birger <eyal.birger@...il.com>, stable
 <stable@...r.kernel.org>, Jann Horn <jannh@...gle.com>, LKML
 <linux-kernel@...r.kernel.org>, linux-trace-kernel
 <linux-trace-kernel@...r.kernel.org>, Linux API
 <linux-api@...r.kernel.org>, X86 ML <x86@...nel.org>, bpf
 <bpf@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar
 <mingo@...hat.com>, Andy Lutomirski <luto@...nel.org>, Deepak Gupta
 <debug@...osinc.com>, Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [PATCHv2 perf/core] uprobes: Harden uretprobe syscall
 trampoline check

On Tue, 11 Feb 2025 17:59:41 +0100
Oleg Nesterov <oleg@...hat.com> wrote:

> On 02/11, Alexei Starovoitov wrote:
> >
> > > > +#define UPROBE_NO_TRAMPOLINE_VADDR ((unsigned long)-1)
> >
> > If you respin anyway maybe use ~0UL instead?
> > In the above and in
> > uprobe_get_trampoline_vaddr(),
> > since
> >
> > unsigned long trampoline_vaddr = -1;
> 
> ... or -1ul in both cases.
> 
> I agree, UPROBE_NO_TRAMPOLINE_VADDR has a single user, looks
> a bit strange...

I think both this function and uprobe_get_trampoline_vaddr()
should use the same macro as a token.
(and ~0UL is a bit more comfortable for me too :) )

----
unsigned long uprobe_get_trampoline_vaddr(void)
{
	struct xol_area *area;
	unsigned long trampoline_vaddr = -1;
----

Thank you,

> 
> Oleg.
> 
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>