linux-kernel - Re: [PATCH v6 5/6] tracing: Show inode and device major:minor in deferred user space stacktrace

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: <20250829130239.61e25379@gandalf.local.home>
Date: Fri, 29 Aug 2025 13:02:39 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Steven Rostedt <rostedt@...nel.org>, Arnaldo Carvalho de Melo
 <arnaldo.melo@...il.com>, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, bpf@...r.kernel.org, x86@...nel.org,
 Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, Josh Poimboeuf <jpoimboe@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, Jiri
 Olsa <jolsa@...nel.org>, Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
 Andrii Nakryiko <andrii@...nel.org>, Indu Bhagat <indu.bhagat@...cle.com>,
 "Jose E. Marchesi" <jemarch@....org>, Beau Belgrave
 <beaub@...ux.microsoft.com>, Jens Remus <jremus@...ux.ibm.com>, Andrew
 Morton <akpm@...ux-foundation.org>, Florian Weimer <fweimer@...hat.com>,
 Sam James <sam@...too.org>, Kees Cook <kees@...nel.org>, "Carlos O'Donell"
 <codonell@...hat.com>
Subject: Re: [PATCH v6 5/6] tracing: Show inode and device major:minor in
 deferred user space stacktrace

On Fri, 29 Aug 2025 09:50:12 -0700
Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> On Fri, 29 Aug 2025 at 09:42, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> >
> > Just use the hash. Don't do anything to it. Don't mess with it.  
> 
> In fact, at actual stack trace time, don't even do the hashing. Just
> save the raw pointer value (but as a *value*, not as a pointer: we
> absolutely do *not* want people to think that the random value can be
> used as a 'struct file' *: it needs to be a plain unsigned long, not
> some kernel pointer).
> 
> Then the hashing can happen when you expose those entries to user
> space (in the "print" stage). At that point you can do that
> 
>        hash = siphash_1u64(value, secret);
> 
> thing.
> 
> That will likely help I$ and D$ too, since you won't be accessing the
> secret hashing data randomly, but do it only at trace output time
> (presumably in a fairly tight loop at that point).

Note, the ring buffer can be mapped to user space. So anything written into
the buffer is already exposed. The "at trace output time" is done by user
space, not the kernel (except when using "trace" and "trace_pipe" files).

-- Steve