linux-kernel - Re: [PATCH v5 20/36] locking/ww_mutex: Support Clang's context analysis

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: <05c77ca1-7618-43c5-b259-d89741808479@acm.org>
Date: Fri, 9 Jan 2026 12:16:33 -0800
From: Bart Van Assche <bvanassche@....org>
To: Marco Elver <elver@...gle.com>, Peter Zijlstra <peterz@...radead.org>,
 Boqun Feng <boqun.feng@...il.com>, Ingo Molnar <mingo@...nel.org>,
 Will Deacon <will@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>,
 Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
 Chris Li <sparse@...isli.org>, "Paul E. McKenney" <paulmck@...nel.org>,
 Alexander Potapenko <glider@...gle.com>, Arnd Bergmann <arnd@...db.de>,
 Christoph Hellwig <hch@....de>, Dmitry Vyukov <dvyukov@...gle.com>,
 Eric Dumazet <edumazet@...gle.com>, Frederic Weisbecker
 <frederic@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Herbert Xu <herbert@...dor.apana.org.au>, Ian Rogers <irogers@...gle.com>,
 Jann Horn <jannh@...gle.com>, Joel Fernandes <joelagnelf@...dia.com>,
 Johannes Berg <johannes.berg@...el.com>, Jonathan Corbet <corbet@....net>,
 Josh Triplett <josh@...htriplett.org>, Justin Stitt
 <justinstitt@...gle.com>, Kees Cook <kees@...nel.org>,
 Kentaro Takeda <takedakn@...data.co.jp>,
 Lukas Bulwahn <lukas.bulwahn@...il.com>, Mark Rutland
 <mark.rutland@....com>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Miguel Ojeda <ojeda@...nel.org>, Nathan Chancellor <nathan@...nel.org>,
 Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
 Steven Rostedt <rostedt@...dmis.org>,
 Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
 Thomas Gleixner <tglx@...utronix.de>, Thomas Graf <tgraf@...g.ch>,
 Uladzislau Rezki <urezki@...il.com>, Waiman Long <longman@...hat.com>,
 kasan-dev@...glegroups.com, linux-crypto@...r.kernel.org,
 linux-doc@...r.kernel.org, linux-kbuild@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 linux-security-module@...r.kernel.org, linux-sparse@...r.kernel.org,
 linux-wireless@...r.kernel.org, llvm@...ts.linux.dev, rcu@...r.kernel.org
Subject: Re: [PATCH v5 20/36] locking/ww_mutex: Support Clang's context
 analysis

On 12/19/25 8:40 AM, Marco Elver wrote:
> Add support for Clang's context analysis for ww_mutex.
> 
> The programming model for ww_mutex is subtly more complex than other
> locking primitives when using ww_acquire_ctx. Encoding the respective
> pre-conditions for ww_mutex lock/unlock based on ww_acquire_ctx state
> using Clang's context analysis makes incorrect use of the API harder.

That's a very short description. It should have been explained in the
patch description how the ww_acquire_ctx changes affect callers of the
ww_acquire_{init,done,fini}() functions.

>   static inline void ww_acquire_init(struct ww_acquire_ctx *ctx,
>   				   struct ww_class *ww_class)
> +	__acquires(ctx) __no_context_analysis
> [ ... ]
>   static inline void ww_acquire_done(struct ww_acquire_ctx *ctx)
> +	__releases(ctx) __acquires_shared(ctx) __no_context_analysis
>   {
> [ ... ]
>   static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx)
> +	__releases_shared(ctx) __no_context_analysis

The above changes make it mandatory to call ww_acquire_done() before
calling ww_acquire_fini(). In Documentation/locking/ww-mutex-design.rst
there is an example where there is no ww_acquire_done() call between
ww_acquire_init() and ww_acquire_fini() (see also line 202). The
function dma_resv_lockdep() in drivers/dma-buf/dma-resv.c doesn't call
ww_acquire_done() at all. Does this mean that the above annotations are
wrong? Is there a better solution than removing the __acquire() and
__release() annotations from the above three functions?

Bart.