On 2013/7/25 22:01, Michal Hocko wrote: > On Wed 24-07-13 11:48:19, Libin wrote: >> find_vma may return NULL, thus check the return >> value to avoid NULL pointer dereference. > > Please add a note that the check matters only because > khugepaged_alloc_page drops mmap_sem. > Thanks for your suggestion. I will add the information and post the patch soon. Regards, Libin. >> Signed-off-by: Libin <huawei.libin@xxxxxxxxxx> > > Other than that > Reviewed-by: Michal Hocko <mhocko@xxxxxxx> > > + I guess this is worth backporting to the stable trees. This goes back > to when khugepaged was introduced AFAICS. > >> --- >> 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>