On Wed, Jul 24, 2013 at 12:22:08PM +0800, Wanpeng Li wrote: >On Wed, Jul 24, 2013 at 11:48:19AM +0800, Libin wrote: >>find_vma may return NULL, thus check the return >>value to avoid NULL pointer dereference. >> > >When can this happen since down_read(&mm->mmap_sem) is held? > Between mmap_sem read lock released and write lock held I think. >>Signed-off-by: Libin <huawei.libin@xxxxxxxxxx> >>--- >> mm/huge_memory.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >>diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>index 243e710..d4423f4 100644 >>--- a/mm/huge_memory.c >>+++ b/mm/huge_memory.c >>@@ -2294,6 +2294,8 @@ static void collapse_huge_page(struct mm_struct *mm, >> goto out; >> >> vma = find_vma(mm, address); >>+ if (!vma) >>+ goto out; >> hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; >> hend = vma->vm_end & HPAGE_PMD_MASK; >> if (address < hstart || address + HPAGE_PMD_SIZE > hend) >>-- >>1.8.2.1 >> >> >>-- >>To unsubscribe, send a message with 'unsubscribe linux-mm' in >>the body to majordomo@xxxxxxxxx. For more info on Linux MM, >>see: http://www.linux-mm.org/ . >>Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> > >-- >To unsubscribe, send a message with 'unsubscribe linux-mm' in >the body to majordomo@xxxxxxxxx. For more info on Linux MM, >see: http://www.linux-mm.org/ . >Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>