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author | Catalin Marinas <catalin.marinas@arm.com> | 2016-08-11 17:44:50 (GMT) |
---|---|---|
committer | Will Deacon <will.deacon@arm.com> | 2016-08-25 17:00:29 (GMT) |
commit | cab15ce604e550020bb7115b779013b91bcdbc21 (patch) | |
tree | 0ba025b8ad16505532aaa6e1b4cc665473f026fa /arch/arm64 | |
parent | 7419333fa15ec958d12845fcc79b7bdd16de06ec (diff) | |
download | linux-cab15ce604e550020bb7115b779013b91bcdbc21.tar.xz |
arm64: Introduce execute-only page access permissions
The ARMv8 architecture allows execute-only user permissions by clearing
the PTE_UXN and PTE_USER bits. However, the kernel running on a CPU
implementation without User Access Override (ARMv8.2 onwards) can still
access such page, so execute-only page permission does not protect
against read(2)/write(2) etc. accesses. Systems requiring such
protection must enable features like SECCOMP.
This patch changes the arm64 __P100 and __S100 protection_map[] macros
to the new __PAGE_EXECONLY attributes. A side effect is that
pte_user() no longer triggers for __PAGE_EXECONLY since PTE_USER isn't
set. To work around this, the check is done on the PTE_NG bit via the
pte_ng() macro. VM_READ is also checked now for page faults.
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64')
-rw-r--r-- | arch/arm64/include/asm/pgtable-prot.h | 5 | ||||
-rw-r--r-- | arch/arm64/include/asm/pgtable.h | 10 | ||||
-rw-r--r-- | arch/arm64/mm/fault.c | 5 |
3 files changed, 10 insertions, 10 deletions
diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h index 39f5252..2142c77 100644 --- a/arch/arm64/include/asm/pgtable-prot.h +++ b/arch/arm64/include/asm/pgtable-prot.h @@ -70,12 +70,13 @@ #define PAGE_COPY_EXEC __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN) #define PAGE_READONLY __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN) #define PAGE_READONLY_EXEC __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN) +#define PAGE_EXECONLY __pgprot(_PAGE_DEFAULT | PTE_NG | PTE_PXN) #define __P000 PAGE_NONE #define __P001 PAGE_READONLY #define __P010 PAGE_COPY #define __P011 PAGE_COPY -#define __P100 PAGE_READONLY_EXEC +#define __P100 PAGE_EXECONLY #define __P101 PAGE_READONLY_EXEC #define __P110 PAGE_COPY_EXEC #define __P111 PAGE_COPY_EXEC @@ -84,7 +85,7 @@ #define __S001 PAGE_READONLY #define __S010 PAGE_SHARED #define __S011 PAGE_SHARED -#define __S100 PAGE_READONLY_EXEC +#define __S100 PAGE_EXECONLY #define __S101 PAGE_READONLY_EXEC #define __S110 PAGE_SHARED_EXEC #define __S111 PAGE_SHARED_EXEC diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index e20bd43..7ba1ceb 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -73,7 +73,7 @@ extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]; #define pte_write(pte) (!!(pte_val(pte) & PTE_WRITE)) #define pte_exec(pte) (!(pte_val(pte) & PTE_UXN)) #define pte_cont(pte) (!!(pte_val(pte) & PTE_CONT)) -#define pte_user(pte) (!!(pte_val(pte) & PTE_USER)) +#define pte_ng(pte) (!!(pte_val(pte) & PTE_NG)) #ifdef CONFIG_ARM64_HW_AFDBM #define pte_hw_dirty(pte) (pte_write(pte) && !(pte_val(pte) & PTE_RDONLY)) @@ -84,8 +84,8 @@ extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]; #define pte_dirty(pte) (pte_sw_dirty(pte) || pte_hw_dirty(pte)) #define pte_valid(pte) (!!(pte_val(pte) & PTE_VALID)) -#define pte_valid_not_user(pte) \ - ((pte_val(pte) & (PTE_VALID | PTE_USER)) == PTE_VALID) +#define pte_valid_global(pte) \ + ((pte_val(pte) & (PTE_VALID | PTE_NG)) == PTE_VALID) #define pte_valid_young(pte) \ ((pte_val(pte) & (PTE_VALID | PTE_AF)) == (PTE_VALID | PTE_AF)) @@ -168,7 +168,7 @@ static inline void set_pte(pte_t *ptep, pte_t pte) * Only if the new pte is valid and kernel, otherwise TLB maintenance * or update_mmu_cache() have the necessary barriers. */ - if (pte_valid_not_user(pte)) { + if (pte_valid_global(pte)) { dsb(ishst); isb(); } @@ -202,7 +202,7 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_val(pte) &= ~PTE_RDONLY; else pte_val(pte) |= PTE_RDONLY; - if (pte_user(pte) && pte_exec(pte) && !pte_special(pte)) + if (pte_ng(pte) && pte_exec(pte) && !pte_special(pte)) __sync_icache_dcache(pte, addr); } diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 05d2bd7..a5f098a 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -251,8 +251,7 @@ static int __do_page_fault(struct mm_struct *mm, unsigned long addr, good_area: /* * Check that the permissions on the VMA allow for the fault which - * occurred. If we encountered a write or exec fault, we must have - * appropriate permissions, otherwise we allow any permission. + * occurred. */ if (!(vma->vm_flags & vm_flags)) { fault = VM_FAULT_BADACCESS; @@ -288,7 +287,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, struct task_struct *tsk; struct mm_struct *mm; int fault, sig, code; - unsigned long vm_flags = VM_READ | VM_WRITE | VM_EXEC; + unsigned long vm_flags = VM_READ | VM_WRITE; unsigned int mm_flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; if (notify_page_fault(regs, esr)) |