Messages in this thread Patches in this message | | | Subject | Re: [PATCH v2 7/7] ARM: mm: Fix PXN process with LPAE feature | From | Kefeng Wang <> | Date | Thu, 3 Jun 2021 17:38:51 +0800 |
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On 2021/6/2 23:58, Russell King (Oracle) wrote: > On Wed, Jun 02, 2021 at 11:13:14PM +0800, Kefeng Wang wrote: >> IFSR format when using the Short-descriptor translation table format >> >> Domain fault 01001 First level 01011 Second level >> >> Permission fault 01101 First level 01111 Second level >> >> IFSR format when using the Long-descriptor translation table format >> >> 0011LL Permission fault. LL bits indicate levelb. >> >> After check the ARM spec, I think for the permission fault, we should panic >> with or without LPAE, will change to > As I explained in one of the previous patches, the page tables that get > used for mapping kernel space are the _tasks_ own page tables. Any new > kernel mappings are lazily copied to the task page tables - such as > when a module is loaded. > > The first time we touch a page, we could end up with a page translation > fault. This will call do_page_fault(), and so with your proposal, > loading a module will potentially cause a kernel panic in this case, > probably leading to systems that panic early during userspace boot.
Could we add some FSR_FS check, only panic when the permission fault, eg,
+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 == ) + return true; +#endif + return false; +} + static int __kprobes do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs) { @@ -255,8 +268,7 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
if (fsr & FSR_LNX_PF) { vm_flags = VM_EXEC; - - if (!user_mode(regs)) + if (is_permission_fault && !user_mode(regs)) die_kernel_fault("execution of memory", mm, addr, fsr, regs); } diff --git a/arch/arm/mm/fault.h b/arch/arm/mm/fault.h index 9ecc2097a87a..187954b4acca 100644 --- a/arch/arm/mm/fault.h +++ b/arch/arm/mm/fault.h @@ -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
and suggestion or proper solution to solve the issue?
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