Commit 5cd08fbf authored Jul 02, 2014 by Jason Baron Committed by Ingo Molnar Jul 16, 2014

sched: Fix static_key race with sched_feat()



As pointed out by Andi Kleen, the usage of static keys can be racy in
sched_feat_disable() vs. sched_feat_enable(). Currently, we first check the
value of keys->enabled, and subsequently update the branch direction. This,
can be racy and can potentially leave the keys in an inconsistent state.

Take the i_mutex around these calls to resolve the race.

Reported-by: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Jason Baron <jbaron@akamai.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: rostedt@goodmis.org
Link: http://lkml.kernel.org/r/9d7780c83db26683955cd01e6bc654ee2586e67f.1404315388.git.jbaron@akamai.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 6e76ea8a

kernel/sched/core.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -245,6 +245,7 @@ sched_feat_write(struct file filp, const char __user ubuf,
		char buf[64];
		char *cmp;
		int i;
		struct inode *inode;

		if (cnt > 63)
		cnt = 63;
		@@ -255,7 +256,11 @@ sched_feat_write(struct file filp, const char __user ubuf,
		buf[cnt] = 0;
		cmp = strstrip(buf);

		/* Ensure the static_key remains in a consistent state */
		inode = file_inode(filp);
		mutex_lock(&inode->i_mutex);
		i = sched_feat_set(cmp);
		mutex_unlock(&inode->i_mutex);
		if (i == __SCHED_FEAT_NR)
		return -EINVAL;

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