Messages in this thread Patch in this message | | | From | Wanpeng Li <> | Subject | [PATCH v7 2/4] mm/vmalloc: fix show vmap_area information race with vmap_area tear down | Date | Wed, 25 Sep 2013 09:02:42 +0800 |
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Changelog: *v4 -> v5: return directly for !VM_VM_AREA case and remove (VM_LAZY_FREE | VM_LAZY_FREEING) check *v5 -> v6: add KOSAKI's ack
There is a race window between vmap_area tear down and show vmap_area information.
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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 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> --- mm/vmalloc.c | 13 +++++-------- 1 files changed, 5 insertions(+), 8 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index f75c2aa..7647e69 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; -- 1.7.5.4
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