Subject: + mm-vmalloc-fix-show-vmap_area-information-race-with-vmap_area-tear-down.patch added to -mm tree
To: liwanp@xxxxxxxxxxxxxxxxxx,iamjoonsoo.kim@xxxxxxx,kosaki.motohiro@xxxxxxxxxxxxxx,rientjes@xxxxxxxxxx,zhangyanfei@xxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Wed, 18 Sep 2013 13:40:10 -0700
The patch titled
Subject: mm/vmalloc: fix show vmap_area information race with vmap_area tear down
has been added to the -mm tree. Its filename is
mm-vmalloc-fix-show-vmap_area-information-race-with-vmap_area-tear-down.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-vmalloc-fix-show-vmap_area-information-race-with-vmap_area-tear-down.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-vmalloc-fix-show-vmap_area-information-race-with-vmap_area-tear-down.patch
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------------------------------------------------------
From: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx>
Subject: mm/vmalloc: fix show vmap_area information race with vmap_area tear down
There is a race window between vmap_area tear down and show vmap_area
information.
A B
remove_vm_area
spin_lock(&vmap_area_lock);
va->vm = NULL;
va->flags &= ~VM_VM_AREA;
spin_unlock(&vmap_area_lock);
spin_lock(&vmap_area_lock);
if (va->flags & (VM_LAZY_FREE | VM_LAZY_FREEZING))
return 0;
if (!(va->flags & VM_VM_AREA)) {
seq_printf(m, "0x%pK-0x%pK %7ld vm_map_ram\n",
(void *)va->va_start, (void *)va->va_end,
va->va_end - va->va_start);
return 0;
}
free_unmap_vmap_area(va);
flush_cache_vunmap
free_unmap_vmap_area_noflush
unmap_vmap_area
free_vmap_area_noflush
va->flags |= VM_LAZY_FREE
The assumption !VM_VM_AREA represents vm_map_ram allocation is introduced
by commit: d4033afd ("mm, vmalloc: iterate vmap_area_list, instead of
vmlist, in vmallocinfo()"). However, !VM_VM_AREA also represents vmap_area
is being tear down in race window mentioned above.
This patch fixes it by not dumping any information for !VM_VM_AREA case
and also remove (VM_LAZY_FREE | VM_LAZY_FREEING) check since they are not
possible for !VM_VM_AREA case.
Signed-off-by: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx>
Suggested-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmalloc.c | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)
diff -puN mm/vmalloc.c~mm-vmalloc-fix-show-vmap_area-information-race-with-vmap_area-tear-down mm/vmalloc.c
--- a/mm/vmalloc.c~mm-vmalloc-fix-show-vmap_area-information-race-with-vmap_area-tear-down
+++ a/mm/vmalloc.c
@@ -2583,16 +2583,13 @@ static int s_show(struct seq_file *m, vo
struct vmap_area *va = p;
struct vm_struct *v;
- if (va->flags & (VM_LAZY_FREE | VM_LAZY_FREEING))
+ /*
+ * s_show can encounter race with remove_vm_area, !VM_VM_AREA on
+ * behalf of vmap area is being tear down or vm_map_ram allocation.
+ */
+ if (!(va->flags & VM_VM_AREA))
return 0;
- if (!(va->flags & VM_VM_AREA)) {
- seq_printf(m, "0x%pK-0x%pK %7ld vm_map_ram\n",
- (void *)va->va_start, (void *)va->va_end,
- va->va_end - va->va_start);
- return 0;
- }
-
v = va->vm;
seq_printf(m, "0x%pK-0x%pK %7ld",
_
Patches currently in -mm which might be from liwanp@xxxxxxxxxxxxxxxxxx are
revert-mm-memory-hotplug-fix-lowmem-count-overflow-when-offline-pages.patch
ksm-remove-redundant-__gfp_zero-from-kcalloc.patch
mm-vmalloc-dont-set-area-caller-twice.patch
mm-vmalloc-revert-mm-vmallocc-emit-the-failure-message-before-return.patch
mm-vmalloc-revert-mm-vmallocc-check-vm_uninitialized-flag-in-s_show-instead-of-show_numa_info.patch
mm-vmalloc-fix-show-vmap_area-information-race-with-vmap_area-tear-down.patch
mm-drop-actor-argument-of-do_generic_file_read.patch
mm-drop-actor-argument-of-do_generic_file_read-fix.patch
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