Commit abc25bbc authored by Wang Kefeng's avatar Wang Kefeng Committed by Russell King (Oracle)
Browse files

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: 1d4d3715 ("ARM: 8235/1: Support for the PXN CPU feature on ARMv7")
Signed-off-by: default avatarKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: default avatarRussell King (Oracle) <rmk+kernel@armlinux.org.uk>
parent 2e707106

arch/arm/mm/fault.c

+19 −1
Original line number Diff line number Diff line
@@ -194,6 +194,19 @@ void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs) 
#define VM_FAULT_BADMAP		0x010000

#define VM_FAULT_BADACCESS	0x020000



static inline bool is_permission_fault(unsigned int fsr)

{

	int fs = fsr_fs(fsr);

#ifdef CONFIG_ARM_LPAE

	if ((fs & FS_PERM_NOLL_MASK) == FS_PERM_NOLL)

		return true;

#else

	if (fs == FS_L1_PERM || fs == FS_L2_PERM)

		return true;

#endif

	return false;

}



static vm_fault_t __kprobes

__do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int flags,

		unsigned long vma_flags, struct pt_regs *regs)
@@ -253,9 +266,14 @@ 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;



		if (is_permission_fault(fsr) && !user_mode(regs))

			die_kernel_fault("execution of memory",

					 mm, addr, fsr, regs);

	}



	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);



	/*

arch/arm/mm/fault.h

+4 −0
Original line number Diff line number Diff line
@@ -14,6 +14,8 @@ 


#ifdef CONFIG_ARM_LPAE

#define FSR_FS_AEA		17

#define FS_PERM_NOLL		0xC

#define FS_PERM_NOLL_MASK	0x3C



static inline int fsr_fs(unsigned int fsr)

{
@@ -21,6 +23,8 @@ static inline int fsr_fs(unsigned int fsr) 
}

#else

#define FSR_FS_AEA		22

#define FS_L1_PERM             0xD

#define FS_L2_PERM             0xF



static inline int fsr_fs(unsigned int fsr)

{