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

commit 354d779307 upstream.

> kernel/sched/autogroup.c:230 proc_sched_autogroup_set_nice() warn: potential spectre issue 'sched_prio_to_weight'

Userspace controls @nice, sanitize the array index.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
pull/10/head
Peter Zijlstra 2018-04-20 15:03:45 +02:00 committed by Greg Kroah-Hartman
parent f2a42c6bca
commit bb0b090d83
1 changed files with 5 additions and 2 deletions
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7
kernel/sched/autogroup.c
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@ -7,6 +7,7 @@
#include <linux/utsname.h>
#include <linux/security.h>
#include <linux/export.h>
#include <linux/nospec.h>
unsigned int __read_mostly sysctl_sched_autogroup_enabled = 1;
static struct autogroup autogroup_default;
@ -213,7 +214,7 @@ int proc_sched_autogroup_set_nice(struct task_struct *p, int nice)
static unsigned long next = INITIAL_JIFFIES;
struct autogroup *ag;
unsigned long shares;
int err;
int err, idx;
if (nice < MIN_NICE || nice > MAX_NICE)
return -EINVAL;
@ -231,7 +232,9 @@ int proc_sched_autogroup_set_nice(struct task_struct *p, int nice)
next = HZ / 10 + jiffies;
ag = autogroup_task_get(p);
shares = scale_load(sched_prio_to_weight[nice + 20]);
idx = array_index_nospec(nice + 20, 40);
shares = scale_load(sched_prio_to_weight[idx]);
down_write(&ag->lock);
err = sched_group_set_shares(ag->tg, shares);