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* [Resend][PATCH] x86/power/64: Always create temporary identity mapping correctly
@ 2016-08-08 13:31 Rafael J. Wysocki
  2016-08-08 13:40 ` Borislav Petkov
  2016-08-09  9:23 ` Jiri Kosina
  0 siblings, 2 replies; 37+ messages in thread
From: Rafael J. Wysocki @ 2016-08-08 13:31 UTC (permalink / raw)
  To: Linux PM list, Thomas Garnier, the arch/x86 maintainers
  Cc: Linux Kernel Mailing List, Yinghai Lu, Thomas Gleixner,
	Ingo Molnar, H . Peter Anvin, Kees Cook, Pavel Machek,
	Kernel Hardening, Borislav Petkov

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

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, rework kernel_ident_mapping_init() to support
unaligned offsets between KVA and PA up to the PMD level and make
set_up_temporary_mappings() use it as approprtiate.

Reported-by: Thomas Garnier <thgarnie@google.com>
Suggested-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Yinghai Lu <yinghai@kernel.org>
---

This is sort of urgent, because hibernation doesn't work with KASLR on x86-64
in 4.8-rc1 AFAICS and this should make them work together again.

Unless anyone sees any problems with it, I'll queue it up for 4.8-rc2.

Thomas, would it be possible to test it with KASLR enabled, please?

Thanks,
Rafael

---
 arch/x86/include/asm/init.h   |    4 ++--
 arch/x86/mm/ident_map.c       |   19 +++++++++++--------
 arch/x86/power/hibernate_64.c |    2 +-
 3 files changed, 14 insertions(+), 11 deletions(-)

Index: linux-pm/arch/x86/include/asm/init.h
===================================================================
--- linux-pm.orig/arch/x86/include/asm/init.h
+++ linux-pm/arch/x86/include/asm/init.h
@@ -5,10 +5,10 @@ struct x86_mapping_info {
 	void *(*alloc_pgt_page)(void *); /* allocate buf for page table */
 	void *context;			 /* context for alloc_pgt_page */
 	unsigned long pmd_flag;		 /* page flag for PMD entry */
-	bool kernel_mapping;		 /* kernel mapping or ident mapping */
+	unsigned long offset;		 /* ident mapping offset */
 };
 
 int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page,
-				unsigned long addr, unsigned long end);
+				unsigned long pstart, unsigned long pend);
 
 #endif /* _ASM_X86_INIT_H */
Index: linux-pm/arch/x86/mm/ident_map.c
===================================================================
--- linux-pm.orig/arch/x86/mm/ident_map.c
+++ linux-pm/arch/x86/mm/ident_map.c
@@ -3,15 +3,17 @@
  * included by both the compressed kernel and the regular kernel.
  */
 
-static void ident_pmd_init(unsigned long pmd_flag, pmd_t *pmd_page,
+static void ident_pmd_init(struct x86_mapping_info *info, pmd_t *pmd_page,
 			   unsigned long addr, unsigned long end)
 {
 	addr &= PMD_MASK;
 	for (; addr < end; addr += PMD_SIZE) {
 		pmd_t *pmd = pmd_page + pmd_index(addr);
 
-		if (!pmd_present(*pmd))
-			set_pmd(pmd, __pmd(addr | pmd_flag));
+		if (pmd_present(*pmd))
+			continue;
+
+		set_pmd(pmd, __pmd((addr - info->offset) | info->pmd_flag));
 	}
 }
 
@@ -30,13 +32,13 @@ static int ident_pud_init(struct x86_map
 
 		if (pud_present(*pud)) {
 			pmd = pmd_offset(pud, 0);
-			ident_pmd_init(info->pmd_flag, pmd, addr, next);
+			ident_pmd_init(info, pmd, addr, next);
 			continue;
 		}
 		pmd = (pmd_t *)info->alloc_pgt_page(info->context);
 		if (!pmd)
 			return -ENOMEM;
-		ident_pmd_init(info->pmd_flag, pmd, addr, next);
+		ident_pmd_init(info, pmd, addr, next);
 		set_pud(pud, __pud(__pa(pmd) | _KERNPG_TABLE));
 	}
 
@@ -44,14 +46,15 @@ static int ident_pud_init(struct x86_map
 }
 
 int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page,
-			      unsigned long addr, unsigned long end)
+			      unsigned long pstart, unsigned long pend)
 {
+	unsigned long addr = pstart + info->offset;
+	unsigned long end = pend + info->offset;
 	unsigned long next;
 	int result;
-	int off = info->kernel_mapping ? pgd_index(__PAGE_OFFSET) : 0;
 
 	for (; addr < end; addr = next) {
-		pgd_t *pgd = pgd_page + pgd_index(addr) + off;
+		pgd_t *pgd = pgd_page + pgd_index(addr);
 		pud_t *pud;
 
 		next = (addr & PGDIR_MASK) + PGDIR_SIZE;
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
@@ -87,7 +87,7 @@ static int set_up_temporary_mappings(voi
 	struct x86_mapping_info info = {
 		.alloc_pgt_page	= alloc_pgt_page,
 		.pmd_flag	= __PAGE_KERNEL_LARGE_EXEC,
-		.kernel_mapping = true,
+		.offset		= __PAGE_OFFSET,
 	};
 	unsigned long mstart, mend;
 	pgd_t *pgd;

^ permalink raw reply	[flat|nested] 37+ messages in thread
end of thread, other threads:[~2016-08-11 21:33 UTC | newest]

Thread overview: 37+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-08-08 13:31 [Resend][PATCH] x86/power/64: Always create temporary identity mapping correctly Rafael J. Wysocki
2016-08-08 13:40 ` Borislav Petkov
2016-08-08 13:54   ` Rafael J. Wysocki
2016-08-08 18:00     ` Thomas Garnier
2016-08-08 20:01       ` Rafael J. Wysocki
2016-08-09  7:02     ` Borislav Petkov
2016-08-09 11:47       ` Rafael J. Wysocki
2016-08-09  9:23 ` Jiri Kosina
2016-08-09 11:56   ` Rafael J. Wysocki
2016-08-09 12:58     ` Jiri Kosina
2016-08-09 13:30       ` Jiri Kosina
2016-08-09 15:00         ` Thomas Garnier
2016-08-09 15:05           ` Jiri Kosina
2016-08-09 16:18             ` Rafael J. Wysocki
2016-08-09 16:27               ` Thomas Garnier
2016-08-09 20:50                 ` Rafael J. Wysocki
2016-08-09 20:02               ` Jiri Kosina
2016-08-09 21:23                 ` Rafael J. Wysocki
2016-08-10  0:21                   ` Rafael J. Wysocki
2016-08-10  7:50                     ` Jiri Kosina
2016-08-10 13:11                       ` Rafael J. Wysocki
2016-08-10 13:18                         ` Jiri Kosina
2016-08-10 14:42                           ` Thomas Garnier
2016-08-10 14:59                             ` Jiri Kosina
2016-08-10 16:35                               ` Borislav Petkov
2016-08-10 16:44                                 ` Thomas Garnier
2016-08-10 21:52                                   ` Jiri Kosina
2016-08-10 21:58                                     ` Rafael J. Wysocki
2016-08-10 20:56                                 ` Rafael J. Wysocki
2016-08-10 21:13                                   ` Rafael J. Wysocki
2016-08-10 21:59                                     ` Jiri Kosina
2016-08-11  0:35                                       ` Rafael J. Wysocki
2016-08-11  1:17                                         ` Thomas Garnier
2016-08-11  1:35                                           ` Rafael J. Wysocki
2016-08-11 18:47                                             ` Thomas Garnier
2016-08-11 21:33                                               ` Rafael J. Wysocki
2016-08-11 21:32                                                 ` Thomas Garnier

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