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x86/vdso: Handle faults on timens page 

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.

Co-developed-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20191112012724.250792-25-dima@arista.com
This commit is contained in:
Dmitry Safonov 2019-11-12 01:27:13 +00:00 committed by Thomas Gleixner
parent afaa7b5ac7
commit af34ebeb86
2 changed files with 54 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
arch/x86/entry/vdso/vma.c
View File

@ -14,11 +14,14 @@
#include <linux/elf.h>
#include <linux/cpu.h>
#include <linux/ptrace.h>
#include <linux/time_namespace.h>
#include <asm/pvclock.h>
#include <asm/vgtod.h>
#include <asm/proto.h>
#include <asm/vdso.h>
#include <asm/vvar.h>
#include <asm/tlb.h>
#include <asm/page.h>
#include <asm/desc.h>
#include <asm/cpufeature.h>
@ -107,10 +110,36 @@ static int vvar_mremap(const struct vm_special_mapping *sm,
return 0;
}
#ifdef CONFIG_TIME_NS
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 inline 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)
{
const struct vdso_image *image = vma->vm_mm->context.vdso_image;
unsigned long pfn;
long sym_offset;
if (!image)
@ -130,8 +159,21 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
return VM_FAULT_SIGBUS;
if (sym_offset == image->sym_vvar_page) {
return vmf_insert_pfn(vma, vmf->address,
__pa_symbol(&__vvar_page) >> PAGE_SHIFT);
struct page *timens_page = find_timens_vvar_page(vma);
pfn = __pa_symbol(&__vvar_page) >> PAGE_SHIFT;
/*
* If a task belongs to a time namespace then a namespace
* specific VVAR is mapped with the sym_vvar_page offset and
* the real VVAR page is mapped with the sym_timens_page
* offset.
* See also the comment near timens_setup_vdso_data().
*/
if (timens_page)
pfn = page_to_pfn(timens_page);
return vmf_insert_pfn(vma, vmf->address, pfn);
} else if (sym_offset == image->sym_pvclock_page) {
struct pvclock_vsyscall_time_info *pvti =
pvclock_get_pvti_cpu0_va();
@ -146,6 +188,14 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
if (tsc_pg && vclock_was_used(VCLOCK_HVCLOCK))
return vmf_insert_pfn(vma, vmf->address,
virt_to_phys(tsc_pg) >> PAGE_SHIFT);
} else if (sym_offset == image->sym_timens_page) {
struct page *timens_page = find_timens_vvar_page(vma);
if (!timens_page)
return VM_FAULT_SIGBUS;
pfn = __pa_symbol(&__vvar_page) >> PAGE_SHIFT;
return vmf_insert_pfn(vma, vmf->address, pfn);
}
return VM_FAULT_SIGBUS;

2
mm/mmap.c
View File

@ -3342,6 +3342,8 @@ static const struct vm_operations_struct special_mapping_vmops = {
.fault = special_mapping_fault,
.mremap = special_mapping_mremap,
.name = special_mapping_name,
/* vDSO code relies that VVAR can't be accessed remotely */
.access = NULL,
};
static const struct vm_operations_struct legacy_special_mapping_vmops = {