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arm64/vdso: Restrict splitting VVAR VMA

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Forbid splitting VVAR VMA resulting in a stricter ABI and reducing the
amount of corner-cases to consider while working further on VDSO time
namespace support.

As the offset from timens to VVAR page is computed compile-time, the pages
in VVAR should stay together and not being partically mremap()'ed.

Signed-off-by: Andrei Vagin <avagin@gmail.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20200624083321.144975-6-avagin@gmail.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Andrei Vagin 2020-06-24 01:33:20 -07:00 committed by Catalin Marinas
parent ee3cda8e46
commit bcf9964342
1 changed files with 13 additions and 0 deletions
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13
arch/arm64/kernel/vdso.c
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@ -223,6 +223,17 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
return vmf_insert_pfn(vma, vmf->address, pfn);
}
static int vvar_mremap(const struct vm_special_mapping *sm,
struct vm_area_struct *new_vma)
{
unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
if (new_size != VVAR_NR_PAGES * PAGE_SIZE)
return -EINVAL;
return 0;
}
static int __setup_additional_pages(enum vdso_abi abi,
struct mm_struct *mm,
struct linux_binprm *bprm,
@ -302,6 +313,7 @@ static struct vm_special_mapping aarch32_vdso_maps[] = {
[AA32_MAP_VVAR] = {
.name = "[vvar]",
.fault = vvar_fault,
.mremap = vvar_mremap,
},
[AA32_MAP_VDSO] = {
.name = "[vdso]",
@ -468,6 +480,7 @@ static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
[AA64_MAP_VVAR] = {
.name = "[vvar]",
.fault = vvar_fault,
.mremap = vvar_mremap,
},
[AA64_MAP_VDSO] = {
.name = "[vdso]",