s390/mm: Fix VM_FAULT_HWPOISON handling in do_exception()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: s390/mm: Fix VM_FAULT_HWPOISON handling in do_exception() There is no support for HWPOISON, MEMORY_FAILURE, or ARCH_HAS_COPY_MC on s390. Therefore we do not expect to see VM_FAULT_HWPOISON in do_exception(). However, since commit af19487f00f3 ("mm: make PTE_MARKER_SWAPIN_ERROR more general"), it is possible to see VM_FAULT_HWPOISON in combination with PTE_MARKER_POISONED, even on architectures that do not support HWPOISON otherwise. In this case, we will end up on the BUG() in do_exception(). Fix this by treating VM_FAULT_HWPOISON the same as VM_FAULT_SIGBUS, similar to x86 when MEMORY_FAILURE is not configured. Also print unexpected fault flags, for easier debugging. Note that VM_FAULT_HWPOISON_LARGE is not expected, because s390 cannot support swap entries on other levels than PTE level.

References

• https://git.kernel.org/stable/c/73a9260b7366d2906ec011e100319359fe2277d0
• https://git.kernel.org/stable/c/9e13767ccefdc4f8aa92514b592b60f6b54882ff
• https://git.kernel.org/stable/c/a3aefb871222a9880602d1a44a558177b4143e3b
• https://git.kernel.org/stable/c/df39038cd89525d465c2c8827eb64116873f141a