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linux/mm
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Mel Gorman b7f50cfa36 mm, page-allocator: do not check the state of a non-existant buddy during free 
There is a bug in commit 6dda9d55 ("page allocator: reduce fragmentation
in buddy allocator by adding buddies that are merging to the tail of the
free lists") that means a buddy at order MAX_ORDER is checked for merging.
 A page of this order never exists so at times, an effectively random
piece of memory is being checked.

Alan Curry has reported that this is causing memory corruption in
userspace data on a PPC32 platform (http://lkml.org/lkml/2010/10/9/32).
It is not clear why this is happening.  It could be a cache coherency
problem where pages mapped in both user and kernel space are getting
different cache lines due to the bad read from kernel space
(http://lkml.org/lkml/2010/10/13/179).  It could also be that there are
some special registers being io-remapped at the end of the memmap array
and that a read has special meaning on them.  Compiler bugs have been
ruled out because the assembly before and after the patch looks relatively
harmless.

This patch fixes the problem by ensuring we are not reading a possibly
invalid location of memory.  It's not clear why the read causes corruption
but one way or the other it is a buggy read.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Cc: Corrado Zoccolo <czoccolo@gmail.com>
Reported-by: Alan Curry <pacman@kosh.dhis.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-10-26 16:52:03 -07:00
..
backing-dev.c bdi: Initialize noop_backing_dev_info properly 2010-09-22 09:48:47 +02:00
bootmem.c x86, memblock: Replace e820_/_early string with memblock_ 2010-08-27 11:13:47 -07:00
bounce.c bounce: call flush_dcache_page() after bounce_copy_vec() 2010-09-09 18:57:25 -07:00
compaction.c mm: compaction: handle active and inactive fairly in too_many_isolated 2010-09-09 18:57:24 -07:00
debug-pagealloc.c
dmapool.c
fadvise.c readahead: introduce FMODE_RANDOM for POSIX_FADV_RANDOM 2010-03-06 11:26:25 -08:00
failslab.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
filemap.c gcc-4.6: mm: fix unused but set warnings 2010-08-09 20:44:58 -07:00
filemap_xip.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
fremap.c Avoid pgoff overflow in remap_file_pages 2010-09-25 09:34:58 -07:00
highmem.c mm,kdb,kgdb: Add a debug reference for the kdb kmap usage 2010-08-05 09:22:24 -05:00
hugetlb.c Encode huge page size for VM_FAULT_HWPOISON errors 2010-10-08 09:32:46 +02:00
hwpoison-inject.c HWPOISON, hugetlb: support hwpoison injection for hugepage 2010-08-11 09:23:11 +02:00
init-mm.c mm: provide init_mm mm_context initializer 2010-08-09 20:44:54 -07:00
internal.h HWPOISON: add an interface to switch off/on all the page filters 2009-12-16 12:19:59 +01:00
Kconfig Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2010-10-22 17:31:36 -07:00
Kconfig.debug trivial: improve help text for mm debug config options 2009-09-21 15:14:57 +02:00
kmemcheck.c kmemcheck: Fix build errors due to missing slab.h 2010-03-30 22:02:32 +09:00
kmemleak-test.c
kmemleak.c kmemleak: Fix typo in the comment 2010-08-08 21:57:23 +01:00
ksm.c ksm: fix bad user data when swapping 2010-10-04 11:09:53 -07:00
maccess.c maccess,probe_kernel: Allow arch specific override probe_kernel_(read|write) 2010-01-07 11:58:36 -06:00
madvise.c HWPOISON: Add a madvise() injector for soft page offlining 2009-12-16 12:20:00 +01:00
Makefile percpu: use percpu allocator on UP too 2010-10-02 10:26:05 +03:00
memblock.c memblock: Annotate memblock functions with __init_memblock 2010-10-11 16:00:52 -07:00
memcontrol.c memcg: fix thresholds with use_hierarchy == 1 2010-10-07 13:31:21 -07:00
memory-failure.c Merge branch 'hwpoison-hugepages' into hwpoison 2010-10-22 17:40:48 +02:00
memory.c Merge branch 'hwpoison-hugepages' into hwpoison 2010-10-22 17:40:48 +02:00
memory_hotplug.c mm: fix return value of scan_lru_pages in memory unplug 2010-10-26 16:52:03 -07:00
mempolicy.c mempolicy: reduce stack size of migrate_pages() 2010-08-09 20:44:58 -07:00
mempool.c mm: remove broken 'kzalloc' mempool 2009-09-22 07:17:35 -07:00
migrate.c Fix migration.c compilation on s390 2010-10-11 16:57:39 +02:00
mincore.c mincore: do nested page table walks 2010-05-25 08:06:58 -07:00
mlock.c mm: Move vma_stack_continue into mm.h 2010-09-09 09:05:06 -07:00
mm_init.c
mmap.c mmap: call unlink_anon_vmas() in __split_vma() in case of error 2010-09-22 17:22:40 -07:00
mmu_context.c exit: fix oops in sync_mm_rss 2010-03-24 16:31:21 -07:00
mmu_notifier.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
mmzone.c mm: page allocator: calculate a better estimate of NR_FREE_PAGES when memory is low and kswapd is awake 2010-09-09 18:57:25 -07:00
mprotect.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
mremap.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
msync.c sanitize vfs_fsync calling conventions 2010-05-21 18:31:21 -04:00
nommu.c mm: make the vma list be doubly linked 2010-08-21 08:49:21 -07:00
oom_kill.c oom: filter unkillable tasks from tasklist dump 2010-09-22 17:22:39 -07:00
page-writeback.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client 2010-08-28 14:07:20 -07:00
page_alloc.c mm, page-allocator: do not check the state of a non-existant buddy during free 2010-10-26 16:52:03 -07:00
page_cgroup.c kmemleak: Annotate false positive in init_section_page_cgroup() 2010-07-19 11:54:14 +01:00
page_io.c block: unify flags for struct bio and struct request 2010-08-07 18:20:39 +02:00
page_isolation.c
pagewalk.c pagemap: fix pfn calculation for hugepage 2010-04-07 08:38:04 -07:00
percpu-km.c percpu: clear memory allocated with the km allocator 2010-10-02 10:28:42 +03:00
percpu-vm.c percpu: move vmalloc based chunk management into percpu-vm.c 2010-05-01 08:30:50 +02:00
percpu.c Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2010-10-24 13:41:39 -07:00
prio_tree.c
quicklist.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
readahead.c readahead.c: fix comment 2010-05-25 08:07:00 -07:00
rmap.c Merge branch 'hwpoison' of git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-mce-2.6 2010-10-26 10:13:10 -07:00
shmem.c shmem: put_super must percpu_counter_destroy 2010-08-17 18:33:11 -07:00
slab.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/slab-2.6 2010-08-22 10:08:52 -07:00
slob.c slob: fix gfp flags for order-0 page allocations 2010-10-02 10:24:28 +03:00
slub.c SLUB: Fix memory hotplug with !NUMA 2010-10-06 21:16:42 +03:00
sparse-vmemmap.c x86: Use memblock to replace early_res 2010-08-27 11:12:29 -07:00
sparse.c sparsemem: on no vmemmap path put mem_map on node high too 2010-05-25 08:06:56 -07:00
swap.c mm: export lru_cache_add_*() to modules 2010-05-25 15:06:06 +02:00
swap_state.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
swapfile.c Merge branch 'v2.6.36-rc8' into for-2.6.37/barrier 2010-10-19 09:13:04 +02:00
thrash.c
truncate.c check ATTR_SIZE contraints in inode_change_ok 2010-08-09 16:47:39 -04:00
util.c export __get_user_pages_fast() function 2010-10-24 10:51:24 +02:00
vmalloc.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2010-10-22 17:31:36 -07:00
vmscan.c Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2010-10-24 13:41:39 -07:00
vmstat.c mm: page allocator: calculate a better estimate of NR_FREE_PAGES when memory is low and kswapd is awake 2010-09-09 18:57:25 -07:00