linux-stable.git/mm, branch linux-2.6.27.y

mm/filemap_xip.c: fix race condition in xip_file_fault()

2012-03-17T13:03:54+00:00

commit 99f02ef1f18631eb0a4e0ea0a3d56878dbcb4b90 upstream.

Fix a race condition that shows in conjunction with xip_file_fault() when
two threads of the same user process fault on the same memory page.

In this case, the race winner will install the page table entry and the
unlucky loser will cause an oops: xip_file_fault calls vm_insert_pfn (via
vm_insert_mixed) which drops out at this check:

	retval = -EBUSY;
	if (!pte_none(*pte))
		goto out_unlock;

The resulting -EBUSY return value will trigger a BUG_ON() in
xip_file_fault.

This fix simply considers the fault as fixed in this case, because the
race winner has successfully installed the pte.

[akpm@linux-foundation.org: use conventional (and consistent) comment layout]
Reported-by: David Sadler 
Signed-off-by: Carsten Otte 
Reported-by: Louis Alex Eisner 
Cc: Hugh Dickins 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman 

Signed-off-by: Willy Tarreau

export __get_user_pages_fast() function

2012-02-11T14:38:12+00:00

commit 45888a0c6edc305495b6bd72a30e66bc40b324c6 upstream.

Backport for stable kernel v2.6.32.y to v2.6.36.y.

Needed for next patch:

 oprofile, x86: Fix nmi-unsafe callgraph support

This function is used by KVM to pin process's page in the atomic context.

Define the 'weak' function to avoid other architecture not support it

Acked-by: Nick Piggin 
Signed-off-by: Xiao Guangrong 
Signed-off-by: Marcelo Tosatti 
Signed-off-by: Robert Richter 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Willy Tarreau

mm: avoid wrapping vm_pgoff in mremap()

2011-04-30T14:53:28+00:00

commit 982134ba62618c2d69fbbbd166d0a11ee3b7e3d8 upstream.

The normal mmap paths all avoid creating a mapping where the pgoff
inside the mapping could wrap around due to overflow.  However, an
expanding mremap() can take such a non-wrapping mapping and make it
bigger and cause a wrapping condition.

Noticed by Robert Swiecki when running a system call fuzzer, where it
caused a BUG_ON() due to terminally confusing the vma_prio_tree code.  A
vma dumping patch by Hugh then pinpointed the crazy wrapped case.

Reported-and-tested-by: Robert Swiecki 
Acked-by: Hugh Dickins 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman 
[wt: 2.6.27 has this code in do_mremap()]

shmem: let shared anonymous be nonlinear again

2011-04-30T14:53:21+00:00

commit bee4c36a5cf5c9f63ce1d7372aa62045fbd16d47 upstream.

Up to 2.6.22, you could use remap_file_pages(2) on a tmpfs file or a
shared mapping of /dev/zero or a shared anonymous mapping.  In 2.6.23 we
disabled it by default, but set VM_CAN_NONLINEAR to enable it on safe
mappings.  We made sure to set it in shmem_mmap() for tmpfs files, but
missed it in shmem_zero_setup() for the others.  Fix that at last.

Reported-by: Kenny Simpson 
Signed-off-by: Hugh Dickins 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: fix possible cause of a page_mapped BUG

2011-04-30T14:53:12+00:00

commit a3e8cc643d22d2c8ed36b9be7d9c9ca21efcf7f7 upstream.

Robert Swiecki reported a BUG_ON(page_mapped) from a fuzzer, punching
a hole with madvise(,, MADV_REMOVE).  That path is under mutex, and
cannot be explained by lack of serialization in unmap_mapping_range().

Reviewing the code, I found one place where vm_truncate_count handling
should have been updated, when I switched at the last minute from one
way of managing the restart_addr to another: mremap move changes the
virtual addresses, so it ought to adjust the restart_addr.

But rather than exporting the notion of restart_addr from memory.c, or
converting to restart_pgoff throughout, simply reset vm_truncate_count
to 0 to force a rescan if mremap move races with preempted truncation.

We have no confirmation that this fixes Robert's BUG,
but it is a fix that's worth making anyway.

Signed-off-by: Hugh Dickins 
Signed-off-by: Linus Torvalds 
Cc: Kerin Millar 
Signed-off-by: Greg Kroah-Hartman

install_special_mapping skips security_file_mmap check.

2011-02-09T21:15:39+00:00

commit 462e635e5b73ba9a4c03913b77138cd57ce4b050 upstream.

The install_special_mapping routine (used, for example, to setup the
vdso) skips the security check before insert_vm_struct, allowing a local
attacker to bypass the mmap_min_addr security restriction by limiting
the available pages for special mappings.

bprm_mm_init() also skips the check, and although I don't think this can
be used to bypass any restrictions, I don't see any reason not to have
the security check.

  $ uname -m
  x86_64
  $ cat /proc/sys/vm/mmap_min_addr
  65536
  $ cat install_special_mapping.s
  section .bss
      resb BSS_SIZE
  section .text
      global _start
      _start:
          mov     eax, __NR_pause
          int     0x80
  $ nasm -D__NR_pause=29 -DBSS_SIZE=0xfffed000 -f elf -o install_special_mapping.o install_special_mapping.s
  $ ld -m elf_i386 -Ttext=0x10000 -Tbss=0x11000 -o install_special_mapping install_special_mapping.o
  $ ./install_special_mapping &
  [1] 14303
  $ cat /proc/14303/maps
  0000f000-00010000 r-xp 00000000 00:00 0                                  [vdso]
  00010000-00011000 r-xp 00001000 00:19 2453665                            /home/taviso/install_special_mapping
  00011000-ffffe000 rwxp 00000000 00:00 0                                  [stack]

It's worth noting that Red Hat are shipping with mmap_min_addr set to
4096.

Signed-off-by: Tavis Ormandy 
Acked-by: Kees Cook 
Acked-by: Robert Swiecki 
[ Changed to not drop the error code - akpm ]
Reviewed-by: James Morris 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Willy Tarreau

mm: fix is_mem_section_removable() page_order BUG_ON check

2010-12-09T21:24:16+00:00

commit 572438f9b52236bd8938b1647cc15e027d27ef55 upstream.

page_order() is called by memory hotplug's user interface to check the
section is removable or not.  (is_mem_section_removable())

It calls page_order() withoug holding zone->lock.
So, even if the caller does

	if (PageBuddy(page))
		ret = page_order(page) ...
The caller may hit BUG_ON().

For fixing this, there are 2 choices.
  1. add zone->lock.
  2. remove BUG_ON().

is_mem_section_removable() is used for some "advice" and doesn't need to
be 100% accurate.  This is_removable() can be called via user program..
We don't want to take this important lock for long by user's request.  So,
this patch removes BUG_ON().

Signed-off-by: KAMEZAWA Hiroyuki 
Acked-by: Wu Fengguang 
Acked-by: Michal Hocko 
Acked-by: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: fix return value of scan_lru_pages in memory unplug

2010-12-09T21:24:16+00:00

commit f8f72ad5396987e05a42cf7eff826fb2a15ff148 upstream.

scan_lru_pages returns pfn. So, it's type should be "unsigned long"
not "int".

Note: I guess this has been work until now because memory hotplug tester's
      machine has not very big memory....
      physical address < 32bit << PAGE_SHIFT.

Reported-by: KOSAKI Motohiro 
Signed-off-by: KAMEZAWA Hiroyuki 
Reviewed-by: KOSAKI Motohiro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

numa: fix slab_node(MPOL_BIND)

2010-12-09T21:24:16+00:00

commit 800416f799e0723635ac2d720ad4449917a1481c upstream.

When a node contains only HighMem memory, slab_node(MPOL_BIND)
dereferences a NULL pointer.

[ This code seems to go back all the way to commit 19770b32609b: "mm:
  filter based on a nodemask as well as a gfp_mask".  Which was back in
  April 2008, and it got merged into 2.6.26.  - Linus ]

Signed-off-by: Eric Dumazet 
Cc: Mel Gorman 
Cc: Christoph Lameter 
Cc: Lee Schermerhorn 
Cc: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

guard page for stacks that grow upwards

2010-10-29T04:04:14+00:00

commit 8ca3eb08097f6839b2206e2242db4179aee3cfb3 upstream.

pa-risc and ia64 have stacks that grow upwards. Check that
they do not run into other mappings. By making VM_GROWSUP
0x0 on architectures that do not ever use it, we can avoid
some unpleasant #ifdefs in check_stack_guard_page().

Signed-off-by: Tony Luck 
Signed-off-by: Linus Torvalds 
Cc: dann frazier 
Signed-off-by: Greg Kroah-Hartman