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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>
This commit is contained in:
Peter Zijlstra 2018-04-20 14:29:51 +02:00 committed by Ingo Molnar
parent b5bf9a90bb
commit 7281c8dec8
1 changed files with 6 additions and 1 deletions
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7
kernel/sched/core.c
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@ -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