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arm64/vdso: Handle faults on timens page

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If a task belongs to a time namespace then the VVAR page which contains
the system wide VDSO data is replaced with a namespace specific page
which has the same layout as the VVAR page.

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/20200624083321.144975-5-avagin@gmail.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Andrei Vagin
2020-06-24 01:33:19 -07:00
committed by Catalin Marinas
parent 3503d56cc7
commit ee3cda8e46
1 changed files with 52 additions and 4 deletions
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56
arch/arm64/kernel/vdso.c
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@@ -18,6 +18,7 @@
#include <linux/sched.h>
#include <linux/signal.h>
#include <linux/slab.h>
#include <linux/time_namespace.h>
#include <linux/timekeeper_internal.h>
#include <linux/vmalloc.h>
#include <vdso/datapage.h>
@@ -164,15 +165,62 @@ int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
mmap_read_unlock(mm);
return 0;
}
static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
{
if (likely(vma->vm_mm == current->mm))
return current->nsproxy->time_ns->vvar_page;
/*
* VM_PFNMAP | VM_IO protect .fault() handler from being called
* through interfaces like /proc/$pid/mem or
* process_vm_{readv,writev}() as long as there's no .access()
* in special_mapping_vmops.
* For more details check_vma_flags() and __access_remote_vm()
*/
WARN(1, "vvar_page accessed remotely");
return NULL;
}
#else
static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
{
return NULL;
}
#endif
static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
struct vm_area_struct *vma, struct vm_fault *vmf)
{
if (vmf->pgoff == 0)
return vmf_insert_pfn(vma, vmf->address,
sym_to_pfn(vdso_data));
return VM_FAULT_SIGBUS;
struct page *timens_page = find_timens_vvar_page(vma);
unsigned long pfn;
switch (vmf->pgoff) {
case VVAR_DATA_PAGE_OFFSET:
if (timens_page)
pfn = page_to_pfn(timens_page);
else
pfn = sym_to_pfn(vdso_data);
break;
#ifdef CONFIG_TIME_NS
case VVAR_TIMENS_PAGE_OFFSET:
/*
* If a task belongs to a time namespace then a namespace
* specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
* the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
* offset.
* See also the comment near timens_setup_vdso_data().
*/
if (!timens_page)
return VM_FAULT_SIGBUS;
pfn = sym_to_pfn(vdso_data);
break;
#endif /* CONFIG_TIME_NS */
default:
return VM_FAULT_SIGBUS;
}
return vmf_insert_pfn(vma, vmf->address, pfn);
}
static int __setup_additional_pages(enum vdso_abi abi,