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Message-ID: <2213000.eZV9GAcFWG@vostro.rjw.lan>
Date: Sun, 07 Aug 2016 03:03:26 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Yinghai Lu <yinghai@...nel.org>, Thomas Garnier <thgarnie@...gle.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>, Kees Cook <keescook@...omium.org>, Pavel Machek <pavel@....cz>, the arch/x86 maintainers <x86@...nel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Linux PM list <linux-pm@...r.kernel.org>, kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v2] x86/power/64: Support unaligned addresses for temporary mapping
On Wednesday, August 03, 2016 11:28:48 PM Rafael J. Wysocki wrote:
> On Wed, Aug 3, 2016 at 8:23 PM, Yinghai Lu <yinghai@...nel.org> wrote:
> > From: Thomas Garnier <thgarnie@...gle.com>
> >
> > Correctly setup the temporary mapping for hibernation. Previous
> > implementation assumed the offset between KVA and PA was aligned on the PGD level.
> > With KASLR memory randomization enabled, the offset is randomized on the PUD
> > level. This change supports unaligned up to PMD.
> >
> > Signed-off-by: Thomas Garnier <thgarnie@...gle.com>
> > [yinghai: change loop to virtual address]
> > Signed-off-by: Yinghai Lu <yinghai@...nel.org>
>
> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
On a second thought, it seems to be better to follow your suggestion to simply
provide a special version of kernel_ident_mapping_init() for hibernation,
because it is sufficiently distinct from the other users of the code in
ident_map.c.
The patch below does just that (lightly tested).
Thomas, can you please test this one too?
Thanks,
Rafael
---
From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Subject: [PATCH] x86/power/64: Always create temporary identity mapping correctly
The low-level resume-from-hibernation code on x86-64 uses
kernel_ident_mapping_init() to create the temoprary identity mapping,
but that function assumes that the offset between kernel virtual
addresses and physical addresses is aligned on the PGD level.
However, with a randomized identity mapping base, it may be aligned
on the PUD level and if that happens, the temporary identity mapping
created by set_up_temporary_mappings() will not reflect the actual
kernel identity mapping and the image restoration will fail as a
result (leading to a kernel panic most of the time).
To fix this problem, provide simplified routines for creating the
temporary identity mapping during resume from hibernation on x86-64
that support unaligned offsets between KVA and PA up to the PMD
level.
Although kernel_ident_mapping_init() might be made work in that
case too, using hibernation-specific code for that is way simpler.
Reported-by: Thomas Garnier <thgarnie@...gle.com>
Suggested-by: Yinghai Lu <yinghai@...nel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
arch/x86/power/hibernate_64.c | 61 ++++++++++++++++++++++++++++++++++++------
1 file changed, 53 insertions(+), 8 deletions(-)
Index: linux-pm/arch/x86/power/hibernate_64.c
===================================================================
--- linux-pm.orig/arch/x86/power/hibernate_64.c
+++ linux-pm/arch/x86/power/hibernate_64.c
@@ -77,18 +77,63 @@ static int set_up_temporary_text_mapping
return 0;
}
-static void *alloc_pgt_page(void *context)
+static void ident_pmd_init(pmd_t *pmd, unsigned long addr, unsigned long end)
{
- return (void *)get_safe_page(GFP_ATOMIC);
+ for (; addr < end; addr += PMD_SIZE)
+ set_pmd(pmd + pmd_index(addr),
+ __pmd((addr - __PAGE_OFFSET) | __PAGE_KERNEL_LARGE_EXEC));
+}
+
+static int ident_pud_init(pud_t *pud, unsigned long addr, unsigned long end)
+{
+ unsigned long next;
+
+ for (; addr < end; addr = next) {
+ pmd_t *pmd;
+
+ pmd = (pmd_t *)get_safe_page(GFP_ATOMIC);
+ if (!pmd)
+ return -ENOMEM;
+
+ next = (addr & PUD_MASK) + PUD_SIZE;
+ if (next > end)
+ next = end;
+
+ ident_pmd_init(pmd, addr & PMD_MASK, next);
+ set_pud(pud + pud_index(addr), __pud(__pa(pmd) | _KERNPG_TABLE));
+ }
+ return 0;
+}
+
+static int ident_mapping_init(pgd_t *pgd, unsigned long mstart, unsigned long mend)
+{
+ unsigned long addr = mstart + __PAGE_OFFSET;
+ unsigned long end = mend + __PAGE_OFFSET;
+ unsigned long next;
+
+ for (; addr < end; addr = next) {
+ pud_t *pud;
+ int result;
+
+ pud = (pud_t *)get_safe_page(GFP_ATOMIC);
+ if (!pud)
+ return -ENOMEM;
+
+ next = (addr & PGDIR_MASK) + PGDIR_SIZE;
+ if (next > end)
+ next = end;
+
+ result = ident_pud_init(pud, addr, next);
+ if (result)
+ return result;
+
+ set_pgd(pgd + pgd_index(addr), __pgd(__pa(pud) | _KERNPG_TABLE));
+ }
+ return 0;
}
static int set_up_temporary_mappings(void)
{
- struct x86_mapping_info info = {
- .alloc_pgt_page = alloc_pgt_page,
- .pmd_flag = __PAGE_KERNEL_LARGE_EXEC,
- .kernel_mapping = true,
- };
unsigned long mstart, mend;
pgd_t *pgd;
int result;
@@ -108,7 +153,7 @@ static int set_up_temporary_mappings(voi
mstart = pfn_mapped[i].start << PAGE_SHIFT;
mend = pfn_mapped[i].end << PAGE_SHIFT;
- result = kernel_ident_mapping_init(&info, pgd, mstart, mend);
+ result = ident_mapping_init(pgd, mstart, mend);
if (result)
return result;
}
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