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x86/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.

Co-developed-by: Andrei Vagin <avagin@openvz.org>
Signed-off-by: Andrei Vagin <avagin@openvz.org>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20191112012724.250792-20-dima@arista.com
This commit is contained in:
Dmitry Safonov 2019-11-12 01:27:08 +00:00 committed by Thomas Gleixner
parent 0efc8bb0bb
commit 6f74acfde2
1 changed files with 13 additions and 0 deletions
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13
arch/x86/entry/vdso/vma.c
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@ -84,6 +84,18 @@ static int vdso_mremap(const struct vm_special_mapping *sm,
return 0;
}
static int vvar_mremap(const struct vm_special_mapping *sm,
struct vm_area_struct *new_vma)
{
const struct vdso_image *image = new_vma->vm_mm->context.vdso_image;
unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
if (new_size != -image->sym_vvar_start)
return -EINVAL;
return 0;
}
static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
struct vm_area_struct *vma, struct vm_fault *vmf)
{
@ -136,6 +148,7 @@ static const struct vm_special_mapping vdso_mapping = {
static const struct vm_special_mapping vvar_mapping = {
.name = "[vvar]",
.fault = vvar_fault,
.mremap = vvar_mremap,
};
/*