Messages in this thread | | | Date | Wed, 2 Jun 2021 11:52:56 +0100 | From | "Russell King (Oracle)" <> | Subject | Re: [PATCH v2 7/7] ARM: mm: Fix PXN process with LPAE feature |
| |
Hi,
On Wed, Jun 02, 2021 at 03:02:46PM +0800, Kefeng Wang wrote: > 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" > > Lets' fix it by adding the check in do_page_fault() and panic > when ARM_LPAE enabled. > > Fixes: 1d4d37159d01 ("ARM: 8235/1: Support for the PXN CPU feature on ARMv7") > Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> > --- > arch/arm/mm/fault.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c > index 7cfa9a59d3ec..279bbeb33b48 100644 > --- a/arch/arm/mm/fault.c > +++ b/arch/arm/mm/fault.c > @@ -257,8 +257,14 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs) > vm_flags = VM_WRITE; > } > > - if (fsr & FSR_LNX_PF) > + if (fsr & FSR_LNX_PF) { > vm_flags = VM_EXEC; > +#ifdef CONFIG_ARM_LPAE > + if (addr && addr < TASK_SIZE && !user_mode(regs)) > + die_kernel_fault("execution of user memory", > + addr, fsr, regs); > +#endif > + }
Do we need to do this test here?
Also, is this really LPAE specific? We have similar protection on 32-bit ARM using domains to disable access to userspace except when the user accessors are being used, so I would expect kernel-mode execution to also cause a fault there.
-- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
| |