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fs:super:get_anon_bdev: fix race condition could cause dev exceed its upper limitation

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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>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Wang YanQing 2015-06-23 18:54:45 +08:00 committed by Al Viro
parent 2adc376c55
commit 1af95de6f0
1 changed files with 1 additions and 1 deletions
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2
fs/super.c
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@ -842,7 +842,7 @@ int get_anon_bdev(dev_t *p)
else if (error) else if (error)
return -EAGAIN; return -EAGAIN;
if (dev == (1 << MINORBITS)) { if (dev >= (1 << MINORBITS)) {
spin_lock(&unnamed_dev_lock); spin_lock(&unnamed_dev_lock);
ida_remove(&unnamed_dev_ida, dev); ida_remove(&unnamed_dev_ida, dev);
if (unnamed_dev_start > dev) if (unnamed_dev_start > dev)