linux/fs/proc
David Rientjes 668f9abbd4 mm: close PageTail race
Commit bf6bddf192 ("mm: introduce compaction and migration for
ballooned pages") introduces page_count(page) into memory compaction
which dereferences page->first_page if PageTail(page).

This results in a very rare NULL pointer dereference on the
aforementioned page_count(page).  Indeed, anything that does
compound_head(), including page_count() is susceptible to racing with
prep_compound_page() and seeing a NULL or dangling page->first_page
pointer.

This patch uses Andrea's implementation of compound_trans_head() that
deals with such a race and makes it the default compound_head()
implementation.  This includes a read memory barrier that ensures that
if PageTail(head) is true that we return a head page that is neither
NULL nor dangling.  The patch then adds a store memory barrier to
prep_compound_page() to ensure page->first_page is set.

This is the safest way to ensure we see the head page that we are
expecting, PageTail(page) is already in the unlikely() path and the
memory barriers are unfortunately required.

Hugetlbfs is the exception, we don't enforce a store memory barrier
during init since no race is possible.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Holger Kiehl <Holger.Kiehl@dwd.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: Rafael Aquini <aquini@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-03-04 07:55:47 -08:00
..
array.c fs/proc/array.c: change do_task_stat() to use while_each_thread() 2014-01-23 16:37:02 -08:00
base.c proc: fix ->f_pos overflows in first_tid() 2014-01-23 16:37:01 -08:00
cmdline.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
consoles.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
cpuinfo.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
devices.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
fd.c proc: make proc_fd_permission() thread-friendly 2013-09-11 15:59:03 -07:00
fd.h proc: Move proc_fd() to fs/proc/fd.h 2013-05-01 17:29:39 -04:00
generic.c proc: set attributes of pde using accessor functions 2014-01-23 16:37:01 -08:00
inode.c procfs: also fix proc_reg_get_unmapped_area() for !MMU case 2013-12-12 18:19:26 -08:00
internal.h proc_fill_cache(): just make instantiate_t return int 2013-06-29 12:57:18 +04:00
interrupts.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
Kconfig kcore: add Kconfig help text 2013-11-13 12:09:33 +09:00
kcore.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
kmsg.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
loadavg.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
Makefile mm, vmalloc: move get_vmalloc_info() to vmalloc.c 2013-04-29 15:54:33 -07:00
meminfo.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
namespaces.c consolidate simple ->d_delete() instances 2013-11-15 22:04:17 -05:00
nommu.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
page.c mm: close PageTail race 2014-03-04 07:55:47 -08:00
proc_devtree.c fs/proc/proc_devtree.c: remove empty /proc/device-tree when no openfirmware exists. 2014-01-23 16:37:01 -08:00
proc_net.c [readdir] convert procfs 2013-06-29 12:56:32 +04:00
proc_sysctl.c Don't pass inode to ->d_hash() and ->d_compare() 2013-06-29 12:57:36 +04:00
proc_tty.c proc: use seq_puts()/seq_putc() where possible 2011-01-13 08:03:16 -08:00
root.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2013-09-07 14:35:32 -07:00
self.c new helper: kfree_put_link() 2013-10-24 23:34:49 -04:00
softirqs.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
stat.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
task_mmu.c seq_file: remove "%n" usage from seq_file users 2013-11-15 09:32:20 +09:00
task_nommu.c seq_file: remove "%n" usage from seq_file users 2013-11-15 09:32:20 +09:00
uptime.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
version.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
vmcore.c vmcore: prevent PT_NOTE p_memsz overflow during header update 2014-02-10 16:01:40 -08:00