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
| ||
|
Date: Thu, 24 Oct 2019 13:02:03 +0200 From: Marco Elver <elver@...gle.com> To: Oleg Nesterov <oleg@...hat.com> Cc: LKMM Maintainers -- Akira Yokosawa <akiyks@...il.com>, Alan Stern <stern@...land.harvard.edu>, Alexander Potapenko <glider@...gle.com>, Andrea Parri <parri.andrea@...il.com>, Andrey Konovalov <andreyknvl@...gle.com>, Andy Lutomirski <luto@...nel.org>, Ard Biesheuvel <ard.biesheuvel@...aro.org>, Arnd Bergmann <arnd@...db.de>, Boqun Feng <boqun.feng@...il.com>, Borislav Petkov <bp@...en8.de>, Daniel Axtens <dja@...ens.net>, Daniel Lustig <dlustig@...dia.com>, Dave Hansen <dave.hansen@...ux.intel.com>, David Howells <dhowells@...hat.com>, Dmitry Vyukov <dvyukov@...gle.com>, "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>, Jade Alglave <j.alglave@....ac.uk>, Joel Fernandes <joel@...lfernandes.org>, Jonathan Corbet <corbet@....net>, Josh Poimboeuf <jpoimboe@...hat.com>, Luc Maranget <luc.maranget@...ia.fr>, Mark Rutland <mark.rutland@....com>, Nicholas Piggin <npiggin@...il.com>, "Paul E. McKenney" <paulmck@...ux.ibm.com>, Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>, Will Deacon <will@...nel.org>, kasan-dev <kasan-dev@...glegroups.com>, linux-arch <linux-arch@...r.kernel.org>, "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>, linux-efi@...r.kernel.org, Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, Linux Memory Management List <linux-mm@...ck.org>, "the arch/x86 maintainers" <x86@...nel.org> Subject: Re: [PATCH v2 1/8] kcsan: Add Kernel Concurrency Sanitizer infrastructure On Wed, 23 Oct 2019 at 18:24, Oleg Nesterov <oleg@...hat.com> wrote: > > On 10/22, Marco Elver wrote: > > > > On Tue, 22 Oct 2019 at 17:49, Oleg Nesterov <oleg@...hat.com> wrote: > > > > > > Just for example. Suppose that task->state = TASK_UNINTERRUPTIBLE, this task > > > does __set_current_state(TASK_RUNNING), another CPU does wake_up_process(task) > > > which does the same UNINTERRUPTIBLE -> RUNNING transition. > > > > > > Looks like, this is the "data race" according to kcsan? > > > > Yes, they are "data races". They are probably not "race conditions" though. > > > > This is a fair distinction to make, and we never claimed to find "race > > conditions" only > > I see, thanks, just wanted to be sure... > > > KCSAN's goal is to find *data races* according to the LKMM. Some data > > races are race conditions (usually the more interesting bugs) -- but > > not *all* data races are race conditions. Those are what are usually > > referred to as "benign", but they can still become bugs on the wrong > > arch/compiler combination. Hence, the need to annotate these accesses > > with READ_ONCE, WRITE_ONCE or use atomic_t: > > Well, if I see READ_ONCE() in the code I want to understand why it was > used. Is it really needed for correctness or we want to shut up kcsan? > Say, why should wait_event(wq, *ptr) use READ_ONCE()? Nevermind, please > forget. > > Btw, why __kcsan_check_watchpoint() does user_access_save() before > try_consume_watchpoint() ? Instrumentation is added in UACCESS regions. Since we do not access user-memory, we do user_access_save to ensure everything is safe (otherwise objtool complains that we do calls to non-whitelisted functions). I will try to optimize this a bit, but we can't avoid it. > Oleg. >
Powered by blists - more mailing lists