Commit 8f281770 authored Jul 09, 2018 by Mathieu Desnoyers Committed by Thomas Gleixner Jul 10, 2018

rseq: Use get_user/put_user rather than __get_user/__put_user



__get_user()/__put_user() is used to read values for address ranges that
were already checked with access_ok() on rseq registration.

It has been recognized that __get_user/__put_user are optimizing the
wrong thing. Replace them by get_user/put_user across rseq instead.

If those end up showing up in benchmarks, the proper approach would be to
use user_access_begin() / unsafe_{get,put}_user() / user_access_end()
anyway.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-api@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Watson <davejwatson@fb.com>
Cc: Paul Turner <pjt@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Chris Lameter <cl@linux.com>
Cc: Ben Maurer <bmaurer@fb.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lkml.kernel.org/r/20180709195155.7654-3-mathieu.desnoyers@efficios.com

parent e96d7135

kernel/rseq.c

+7 −7

Original line number	Diff line number	Diff line
		@@ -85,9 +85,9 @@ static int rseq_update_cpu_id(struct task_struct *t)
		{
		u32 cpu_id = raw_smp_processor_id();

		if (__put_user(cpu_id, &t->rseq->cpu_id_start))
		if (put_user(cpu_id, &t->rseq->cpu_id_start))
		return -EFAULT;
		if (__put_user(cpu_id, &t->rseq->cpu_id))
		if (put_user(cpu_id, &t->rseq->cpu_id))
		return -EFAULT;
		trace_rseq_update(t);
		return 0;
		@@ -100,14 +100,14 @@ static int rseq_reset_rseq_cpu_id(struct task_struct *t)
		/*
		* Reset cpu_id_start to its initial state (0).
		*/
		if (__put_user(cpu_id_start, &t->rseq->cpu_id_start))
		if (put_user(cpu_id_start, &t->rseq->cpu_id_start))
		return -EFAULT;
		/*
		* Reset cpu_id to RSEQ_CPU_ID_UNINITIALIZED, so any user coming
		* in after unregistration can figure out that rseq needs to be
		* registered again.
		*/
		if (__put_user(cpu_id, &t->rseq->cpu_id))
		if (put_user(cpu_id, &t->rseq->cpu_id))
		return -EFAULT;
		return 0;
		}
		@@ -120,7 +120,7 @@ static int rseq_get_rseq_cs(struct task_struct t, struct rseq_cs rseq_cs)
		u32 sig;
		int ret;

		ret = __get_user(ptr, &t->rseq->rseq_cs);
		ret = get_user(ptr, &t->rseq->rseq_cs);
		if (ret)
		return ret;
		if (!ptr) {
		@@ -163,7 +163,7 @@ static int rseq_need_restart(struct task_struct *t, u32 cs_flags)
		int ret;

		/* Get thread flags. */
		ret = __get_user(flags, &t->rseq->flags);
		ret = get_user(flags, &t->rseq->flags);
		if (ret)
		return ret;

		@@ -203,7 +203,7 @@ static int clear_rseq_cs(struct task_struct *t)
		*
		* Set rseq_cs to NULL with single-copy atomicity.
		*/
		return __put_user(0UL, &t->rseq->rseq_cs);
		return put_user(0UL, &t->rseq->rseq_cs);
		}

		/*

Admin message