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authorMiklos Szeredi <mszeredi@suse.cz>2011-02-24 14:45:41 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2011-02-24 16:54:21 (GMT)
commit3c522cedb572bb8d2e4867f358bdaa7d0c53d88c (patch)
treeb348cabd2574638702f9abcccd0b8b711b136162
parentdcace5ac85c628af21878a1fa151e5e6403fb8eb (diff)
block: fix refcounting in BLKBSZSET
Adam Kovari and others reported that disconnecting an USB drive with an ntfs-3g filesystem would cause "kernel BUG at fs/inode.c:1421!" to be triggered. The BUG could be traced back to ioctl(BLKBSZSET), which would erroneously decrement the refcount on the bdev. This is because blkdev_get() expects the refcount to be already incremented and either returns success or decrements the refcount and returns an error. The bug was introduced by e525fd89 (block: make blkdev_get/put() handle exclusive access), which didn't take into account this behavior of blkdev_get(). This fixes https://bugzilla.kernel.org/show_bug.cgi?id=29202 (and likely 29792 too) Reported-by: Adam Kovari <kovariadam@gmail.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--block/ioctl.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/block/ioctl.c b/block/ioctl.c
index 9049d46..1124cd2 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -294,9 +294,11 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
return -EINVAL;
if (get_user(n, (int __user *) arg))
return -EFAULT;
- if (!(mode & FMODE_EXCL) &&
- blkdev_get(bdev, mode | FMODE_EXCL, &bdev) < 0)
- return -EBUSY;
+ if (!(mode & FMODE_EXCL)) {
+ bdgrab(bdev);
+ if (blkdev_get(bdev, mode | FMODE_EXCL, &bdev) < 0)
+ return -EBUSY;
+ }
ret = set_blocksize(bdev, n);
if (!(mode & FMODE_EXCL))
blkdev_put(bdev, mode | FMODE_EXCL);

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