Commits
David Hildenbrand committed 689dacb2b09
device-dax: don't leak kernel memory to user space after unloading kmem
commit 60858c00e5f018eda711a3aa84cf62214ef62d61 upstream.
Assume we have kmem configured and loaded:
[root@localhost ~]# cat /proc/iomem
...
140000000-33fffffff : Persistent Memory$
140000000-1481fffff : namespace0.0
150000000-33fffffff : dax0.0
150000000-33fffffff : System RAM
Assume we try to unload kmem. This force-unloading will work, even if
memory cannot get removed from the system.
[root@localhost ~]# rmmod kmem
[ 86.380228] removing memory fails, because memory [0x0000000150000000-0x0000000157ffffff] is onlined
...
[ 86.431225] kmem dax0.0: DAX region [mem 0x150000000-0x33fffffff] cannot be hotremoved until the next reboot
Now, we can reconfigure the namespace:
[root@localhost ~]# ndctl create-namespace --force --reconfig=namespace0.0 --mode=devdax
[ 131.409351] nd_pmem namespace0.0: could not reserve region [mem 0x140000000-0x33fffffff]dax
[ 131.410147] nd_pmem: probe of namespace0.0 failed with error -16namespace0.0 --mode=devdax
...
This fails as expected due to the busy memory resource, and the memory
cannot be used. However, the dax0.0 device is removed, and along its
name.
The name of the memory resource now points at freed memory (name of the
device):
[root@localhost ~]# cat /proc/iomem
...
140000000-33fffffff : Persistent Memory
140000000-1481fffff : namespace0.0
150000000-33fffffff : �_�^7_��/_��wR��WQ���^��� ...
150000000-33fffffff : System RAM
We have to make sure to duplicate the string. While at it, remove the
superfluous setting of the name and fixup a stale comment.
Fixes: 9f960da72b25 ("device-dax: "Hotremove" persistent memory that is used like normal RAM")
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: <stable@vger.kernel.org> [5.3]
Link: http://lkml.kernel.org/r/20200508084217.9160-2-david@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>