sysfs: fix use-after-free in sysfs_kill_sb()

While restructuring the [u]mount path, 4b93dc9b1c68 ("sysfs, kernfs:
prepare mount path for kernfs") incorrectly updated sysfs_kill_sb() so
that it first kills super_block and then tries to dereference its
namespace tag to drop it.  Fix it by caching namespace tag before
killing the superblock and then drop the cached namespace tag.

Signed-off-by: Tejun Heo <[email protected]>
Reported-by: Yuanhan Liu <[email protected]>
Tested-by: Yuanhan Liu <[email protected]>
Tested-by: Vlastimil Babka <[email protected]>
Link: http://lkml.kernel.org/g/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

0 files changed, 0 insertions, 0 deletions