On Tue, Jul 15, 2014 at 2:55 PM, Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> wrote: > Konstantin Khlebnikov wrote: >> It seems boundng logic in do_fault_around is wrong: >> >> start_addr = max(address & fault_around_mask(), vma->vm_start); >> off = ((address - start_addr) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1); >> pte -= off; >> pgoff -= off; >> >> Ok, off <= 511, but it might be bigger than pte offset in pte table. > > I don't see how it possible: fault_around_mask() cannot be more than 0x1ff000 > (x86-64, fault_around_bytes == 2M). It means start_addr will be aligned to 2M > boundary in this case which is start of the page table pte belong to. > > Do I miss something? Nope, you're right. This fixes kernel crash but not the original problem. Problem is caused by calling do_fault_around for _non-linear_ faiult. In this case pgoff is shifted and might become negative during calculation. I'll send another patch. > > -- > Kirill A. Shutemov -- 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>