zfsonlinux/zfs — pull request #1543 by dweeezil (2013-06-25 03:05:57+00:00)
Title: zfs receive -> unable to handle kernel NULL pointer dereference

Fix a pair of conditions in which a concurrent umount can cause
NULl pointer dereferences:

zfs_sb_teardown - prevent a NULL dereference by not calling
dmu_objset_pool with a null z_os.

zfs_resume_fs - don't try to unmount with a null z_os.	This
change makes the ZoL code more consistent with both Illumos
and FreeBSD.