fs:super:get_anon_bdev: fix race condition could cause dev exceed its upper limitation
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Message ID 20150623105445.GA6746@udknight.ahead-top.com
State New
Headers show

Commit Message

wang yanqing June 23, 2015, 10:54 a.m. UTC
Execution of get_anon_bdev concurrently and preemptive kernel all
could bring race condition, it isn't enough to check dev against
its upper limitation with equality operator only.

This patch fix it.

Signed-off-by: Wang YanQing <udknight@gmail.com>
---
 fs/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Patch
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diff --git a/fs/super.c b/fs/super.c
index 928c20f..b613723 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -842,7 +842,7 @@  int get_anon_bdev(dev_t *p)
 	else if (error)
 		return -EAGAIN;
 
-	if (dev == (1 << MINORBITS)) {
+	if (dev >= (1 << MINORBITS)) {
 		spin_lock(&unnamed_dev_lock);
 		ida_remove(&unnamed_dev_ida, dev);
 		if (unnamed_dev_start > dev)