Commit 7281c8de authored Apr 20, 2018 by Peter Zijlstra Committed by Ingo Molnar May 05, 2018

sched/core: Fix possible Spectre-v1 indexing for sched_prio_to_weight[]



> kernel/sched/core.c:6921 cpu_weight_nice_write_s64() warn: potential spectre issue 'sched_prio_to_weight'

Userspace controls @nice, so sanitize the value before using it to
index an array.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent b5bf9a90

kernel/sched/core.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -8,6 +8,7 @@
		#include "sched.h"

		#include <linux/kthread.h>
		#include <linux/nospec.h>

		#include <asm/switch_to.h>
		#include <asm/tlb.h>
		@@ -6923,11 +6924,15 @@ static int cpu_weight_nice_write_s64(struct cgroup_subsys_state *css,
		struct cftype *cft, s64 nice)
		{
		unsigned long weight;
		int idx;

		if (nice < MIN_NICE \|\| nice > MAX_NICE)
		return -ERANGE;

		weight = sched_prio_to_weight[NICE_TO_PRIO(nice) - MAX_RT_PRIO];
		idx = NICE_TO_PRIO(nice) - MAX_RT_PRIO;
		idx = array_index_nospec(idx, 40);
		weight = sched_prio_to_weight[idx];

		return sched_group_set_shares(css_tg(css), scale_load(weight));
		}
		#endif