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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>
This commit is contained in:
Wang Kefeng 2021-09-22 14:56:32 +01:00 committed by Russell King (Oracle)
parent 2e707106fa
commit abc25bbcb5
2 changed files with 23 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
arch/arm/mm/fault.c
View File

@ -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);
/*

4
arch/arm/mm/fault.h
View File

@ -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)
{