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| author | Wanpeng Li <liwanp@linux.vnet.ibm.com> | 2013-11-12 15:07:31 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-11-13 12:09:05 +0900 |
| commit | c2ce8c142c43c360047e173d2018d94a4d0f7a59 (patch) | |
| tree | 089e2f2e337d599380ca48fe5dbc625699ea91ce /mm/vmalloc.c | |
| parent | 3722e13cff361035583f6ecfa784437b824fe659 (diff) | |
| download | linux-c2ce8c142c43c360047e173d2018d94a4d0f7a59.tar.gz linux-c2ce8c142c43c360047e173d2018d94a4d0f7a59.tar.bz2 linux-c2ce8c142c43c360047e173d2018d94a4d0f7a59.zip | |
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 d4033afdf828 ("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 fix it by don't dump 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.
Suggested-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/vmalloc.c')
| -rw-r--r-- | mm/vmalloc.c | 13 |
1 files changed, 5 insertions, 8 deletions
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 285f0e7d28e7..814ce9122709 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2578,15 +2578,12 @@ static int s_show(struct seq_file *m, void *p) struct vmap_area *va = p; struct vm_struct *v; - if (va->flags & (VM_LAZY_FREE | VM_LAZY_FREEING)) - 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); + /* + * 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; - } v = va->vm; |