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authorWanpeng Li <liwanp@linux.vnet.ibm.com>2013-11-12 15:07:31 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2013-11-13 12:09:05 +0900
commitc2ce8c142c43c360047e173d2018d94a4d0f7a59 (patch)
tree089e2f2e337d599380ca48fe5dbc625699ea91ce
parent3722e13cff361035583f6ecfa784437b824fe659 (diff)
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>
-rw-r--r--mm/vmalloc.c13
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;