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: Fri, 4 Feb 2022 18:55:17 +0000 From: Catalin Marinas <catalin.marinas@....com> To: Valentin Schneider <valentin.schneider@....com> Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-rt-users@...r.kernel.org, Sebastian Andrzej Siewior <bigeasy@...utronix.de>, Will Deacon <will@...nel.org>, Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>, Steven Rostedt <rostedt@...dmis.org>, Daniel Bristot de Oliveira <bristot@...hat.com>, "Paul E. McKenney" <paulmck@...nel.org>, Frederic Weisbecker <frederic@...nel.org>, Josh Triplett <josh@...htriplett.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Davidlohr Bueso <dave@...olabs.net>, Lai Jiangshan <jiangshanlai@...il.com>, Joel Fernandes <joel@...lfernandes.org>, Anshuman Khandual <anshuman.khandual@....com>, Vincenzo Frascino <vincenzo.frascino@....com>, Steven Price <steven.price@....com>, Ard Biesheuvel <ardb@...nel.org>, Boqun Feng <boqun.feng@...il.com>, Mike Galbraith <efault@....de> Subject: Re: [PATCH v4] arm64: mm: Make arch_faults_on_old_pte() check for migratability On Thu, Jan 27, 2022 at 07:24:37PM +0000, Valentin Schneider wrote: > arch_faults_on_old_pte() relies on the calling context being > non-preemptible. CONFIG_PREEMPT_RT turns the PTE lock into a sleepable > spinlock, which doesn't disable preemption once acquired, triggering the > warning in arch_faults_on_old_pte(). > > It does however disable migration, ensuring the task remains on the same > CPU during the entirety of the critical section, making the read of > cpu_has_hw_af() safe and stable. > > Make arch_faults_on_old_pte() check cant_migrate() instead of preemptible(). > > Suggested-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de> > Signed-off-by: Valentin Schneider <valentin.schneider@....com> > Link: https://lore.kernel.org/r/20210811201354.1976839-5-valentin.schneider@arm.com > --- > v3 -> v4: Dropped migratable(), reuse cant_migrate() (Sebastian) > --- > arch/arm64/include/asm/pgtable.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index c4ba047a82d2..3caf6346ea95 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -1001,7 +1001,8 @@ static inline void update_mmu_cache(struct vm_area_struct *vma, > */ > static inline bool arch_faults_on_old_pte(void) > { > - WARN_ON(preemptible()); > + /* The register read below requires a stable CPU to make any sense */ > + cant_migrate(); > > return !cpu_has_hw_af(); > } The patch looks alright but what's the plan with it? Does it go into the preempt-rt tree, mainline? It's not a fix to be queued now, so: Acked-by: Catalin Marinas <catalin.marinas@....com>
Powered by blists - more mailing lists