A USB stick with a ext file system on it, would occasionally crash when the stick was pulled. The problem was a timer was being set on the Backing Device Interface, bdi, after the USB device had been removed and the bdi had been unregistered. The bdi would then be later reinitialized by zeroing the timer without removing from the timer from the timer queue. This would eventually result in a kernel crash (NULL ptr dereference). When the bdi is unregistered, the dev field is set to NULL. This indication is used by bdi_unregister to only unregister the device once. Fix: When the backing device is invalidated, the mapping backing_dev_info should be redirected to the default_backing_dev_info. Created 3 USB sticks with ext2, ext4 and one with both apple and DOS file systems on it. Inserted and removed USB sticks many times in random order. With out the bug fix, the kernel would soon crash. With the fix, it did not. Ran on both stumpy and amd64-generic. Signed-off-by: Paul Taysom <taysom@xxxxxxxxxxxx> Cc: Mandeep Baines <msb@xxxxxxxxxxxx> Cc: Greg KH <greg@xxxxxxxxx> Cc: Jens Axboe <axboe@xxxxxxxxx> Cc: Theodore Tso <tytso@xxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxx> Cc: <linux-usb@xxxxxxxxxxxxxxx> Cc: <linux-kernel@xxxxxxxxxxxxxxx> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: <linux-fsdevel@xxxxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxx> --- fs/block_dev.c | 1 + 1 files changed, 1 insertions(+), 0 deletions(-) diff --git a/fs/block_dev.c b/fs/block_dev.c index afe74dd..322cd05 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -110,6 +110,7 @@ void invalidate_bdev(struct block_device *bdev) * But, for the strange corners, lets be cautious */ cleancache_flush_inode(mapping); + mapping->backing_dev_info = &default_backing_dev_info; } EXPORT_SYMBOL(invalidate_bdev); -- 1.7.7.3 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
