Commit 1b6867d2 authored by Andrei Vagin's avatar Andrei Vagin Committed by Catalin Marinas

arm64/vdso: Zap vvar pages when switching to a time namespace

The order of vvar pages depends on whether a task belongs to the root
time namespace or not. In the root time namespace, a task doesn't have a
per-namespace page. In a non-root namespace, the VVAR page which contains
the system-wide VDSO data is replaced with a namespace specific page
that contains clock offsets.

Whenever a task changes its namespace, the VVAR page tables are cleared
and then they will be re-faulted with a corresponding layout.

A task can switch its time namespace only if its ->mm isn't shared with
another task.
Signed-off-by: default avatarAndrei Vagin <avagin@gmail.com>
Reviewed-by: default avatarVincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: default avatarDmitry Safonov <dima@arista.com>
Reviewed-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/20200624083321.144975-3-avagin@gmail.comSigned-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent d53b5c01
...@@ -124,6 +124,37 @@ static int __vdso_init(enum vdso_abi abi) ...@@ -124,6 +124,37 @@ static int __vdso_init(enum vdso_abi abi)
return 0; return 0;
} }
#ifdef CONFIG_TIME_NS
/*
* The vvar mapping contains data for a specific time namespace, so when a task
* changes namespace we must unmap its vvar data for the old namespace.
* Subsequent faults will map in data for the new namespace.
*
* For more details see timens_setup_vdso_data().
*/
int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
{
struct mm_struct *mm = task->mm;
struct vm_area_struct *vma;
mmap_read_lock(mm);
for (vma = mm->mmap; vma; vma = vma->vm_next) {
unsigned long size = vma->vm_end - vma->vm_start;
if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm))
zap_page_range(vma, vma->vm_start, size);
#ifdef CONFIG_COMPAT_VDSO
if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm))
zap_page_range(vma, vma->vm_start, size);
#endif
}
mmap_read_unlock(mm);
return 0;
}
#endif
static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
struct vm_area_struct *vma, struct vm_fault *vmf) struct vm_area_struct *vma, struct vm_fault *vmf)
{ {
......
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