From mboxrd@z Thu Jan 1 00:00:00 1970 From: mark.rutland@arm.com (Mark Rutland) Date: Mon, 31 Jul 2017 11:24:14 +0100 Subject: [PATCH] arm64: mmu: Place guard page after mapping of kernel image In-Reply-To: <1501175035-32460-1-git-send-email-will.deacon@arm.com> References: <1501175035-32460-1-git-send-email-will.deacon@arm.com> Message-ID: <20170731102414.GB21287@remoulade> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Jul 27, 2017 at 06:03:55PM +0100, Will Deacon wrote: > The vast majority of virtual allocations in the vmalloc region are followed > by a guard page, which can help to avoid overruning on vma into another, > which may map a read-sensitive device. > > This patch adds a guard page to the end of the kernel image mapping (i.e. > following the data/bss segments). > > Cc: Mark Rutland > Cc: Ard Biesheuvel > Signed-off-by: Will Deacon Looks sane to me. Acked-by: Mark Rutland Mark. > --- > arch/arm64/mm/mmu.c | 18 +++++++++++------- > 1 file changed, 11 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 23c2d89a362e..f1eb15e0e864 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -496,7 +496,7 @@ void mark_rodata_ro(void) > > static void __init map_kernel_segment(pgd_t *pgd, void *va_start, void *va_end, > pgprot_t prot, struct vm_struct *vma, > - int flags) > + int flags, unsigned long vm_flags) > { > phys_addr_t pa_start = __pa_symbol(va_start); > unsigned long size = va_end - va_start; > @@ -507,10 +507,13 @@ static void __init map_kernel_segment(pgd_t *pgd, void *va_start, void *va_end, > __create_pgd_mapping(pgd, pa_start, (unsigned long)va_start, size, prot, > early_pgtable_alloc, flags); > > + if (!(vm_flags & VM_NO_GUARD)) > + size += PAGE_SIZE; > + > vma->addr = va_start; > vma->phys_addr = pa_start; > vma->size = size; > - vma->flags = VM_MAP; > + vma->flags = VM_MAP | vm_flags; > vma->caller = __builtin_return_address(0); > > vm_area_add_early(vma); > @@ -541,14 +544,15 @@ static void __init map_kernel(pgd_t *pgd) > * Only rodata will be remapped with different permissions later on, > * all other segments are allowed to use contiguous mappings. > */ > - map_kernel_segment(pgd, _text, _etext, text_prot, &vmlinux_text, 0); > + map_kernel_segment(pgd, _text, _etext, text_prot, &vmlinux_text, 0, > + VM_NO_GUARD); > map_kernel_segment(pgd, __start_rodata, __inittext_begin, PAGE_KERNEL, > - &vmlinux_rodata, NO_CONT_MAPPINGS); > + &vmlinux_rodata, NO_CONT_MAPPINGS, VM_NO_GUARD); > map_kernel_segment(pgd, __inittext_begin, __inittext_end, text_prot, > - &vmlinux_inittext, 0); > + &vmlinux_inittext, 0, VM_NO_GUARD); > map_kernel_segment(pgd, __initdata_begin, __initdata_end, PAGE_KERNEL, > - &vmlinux_initdata, 0); > - map_kernel_segment(pgd, _data, _end, PAGE_KERNEL, &vmlinux_data, 0); > + &vmlinux_initdata, 0, VM_NO_GUARD); > + map_kernel_segment(pgd, _data, _end, PAGE_KERNEL, &vmlinux_data, 0, 0); > > if (!pgd_val(*pgd_offset_raw(pgd, FIXADDR_START))) { > /* > -- > 2.1.4 >