Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

device-dax: correct pgoff align in dax_set_mapping()

pgoff should be aligned using ALIGN_DOWN() instead of ALIGN(). Otherwise, vmf->address not aligned to fault_size will be aligned to the next alignment, that can result in memory failure getting the wrong address.

It's a subtle situation that only can be observed in page_mapped_in_vma() after the page is page fault handled by dev_dax_huge_fault. Generally, there is little chance to perform page_mapped_in_vma in dev-dax's page unless in specific error injection to the dax device to trigger an MCE - memory-failure. In that case, page_mapped_in_vma() will be triggered to determine which task is accessing the failure address and kill that task in the end.

We used self-developed dax device (which is 2M aligned mapping) , to perform error injection to random address. It turned out that error injected to non-2M-aligned address was causing endless MCE until panic. Because page_mapped_in_vma() kept resulting wrong address and the task accessing the failure address was never killed properly:

[ 3783.719419] Memory failure: 0x200c9742: recovery action for dax page: Recovered [ 3784.049006] mce: Uncorrected hardware memory error in user-access at 200c9742380 [ 3784.049190] Memory failure: 0x200c9742: recovery action for dax page: Recovered [ 3784.448042] mce: Uncorrected hardware memory error in user-access at 200c9742380 [ 3784.448186] Memory failure: 0x…