Wang Kefeng abc25bbcb5 ARM: 9131/1: mm: Fix PXN process with LPAE feature ...

When user code execution with privilege mode, it will lead to
infinite loop in the page fault handler if ARM_LPAE enabled,

The issue could be reproduced with
  "echo EXEC_USERSPACE > /sys/kernel/debug/provoke-crash/DIRECT"

As Permission fault shows in ARM spec,
  IFSR format when using the Short-descriptor translation table format
    Permission fault:       01101 First level      01111 Second level
  IFSR format when using the Long-descriptor translation table format
    Permission fault:       0011LL LL bits indicate levelb.

Add is_permission_fault() function to check permission fault and die
if permission fault occurred under instruction fault in do_page_fault().

Fixes: 1d4d37159d ("ARM: 8235/1: Support for the PXN CPU feature on ARMv7")
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

2021-10-19 10:35:43 +01:00

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