Commit-ID: 5cd08fbfdb6baa9fe98f530b76898fc5725a6289 Gitweb: http://git.kernel.org/tip/5cd08fbfdb6baa9fe98f530b76898fc5725a6289 Author: Jason Baron <jbaron@xxxxxxxxxx> AuthorDate: Wed, 2 Jul 2014 15:52:44 +0000 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Wed, 16 Jul 2014 13:38:21 +0200 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@xxxxxxxxxxxxxx> Signed-off-by: Jason Baron <jbaron@xxxxxxxxxx> Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: rostedt@xxxxxxxxxxx Link: http://lkml.kernel.org/r/9d7780c83db26683955cd01e6bc654ee2586e67f.1404315388.git.jbaron@xxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- kernel/sched/core.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 2f96081..8705125 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -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; -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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