linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: ira.weiny@intel.com
To: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>
Cc: Ira Weiny <ira.weiny@intel.com>,
	x86@kernel.org, Dave Hansen <dave.hansen@linux.intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Vishal Verma <vishal.l.verma@intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Fenghua Yu <fenghua.yu@intel.com>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-nvdimm@lists.01.org, linux-fsdevel@vger.kernel.org,
	linux-mm@kvack.org, linux-kselftest@vger.kernel.org
Subject: [PATCH RFC V2 13/17] kmap: Add stray write protection for device pages
Date: Fri, 17 Jul 2020 00:20:52 -0700	[thread overview]
Message-ID: <20200717072056.73134-14-ira.weiny@intel.com> (raw)
In-Reply-To: <20200717072056.73134-1-ira.weiny@intel.com>

From: Ira Weiny <ira.weiny@intel.com>

Device managed pages may have additional protections.  These protections
need to be removed prior to valid use by kernel users.

Check for special treatment of device managed pages in kmap and take
action if needed.  We use kmap as an interface for generic kernel code
because under normal circumstances it would be a bug for general kernel
code to not use kmap prior to accessing kernel memory.  Therefore, this
should allow any valid kernel users to seamlessly use these pages
without issues.

Because of the critical nature of kmap it must be pointed out that the
over head on regular DRAM is carefully implemented to be as fast as
possible.  Furthermore the underlying MSR write required on device pages
when protected is better than a normal MSR write.

Specifically, WRMSR(MSR_IA32_PKRS) is not serializing but still
maintains ordering properties similar to WRPKRU.  The current SDM
section on PKRS needs updating but should be the same as that of WRPKRU.
So to quote from the WRPKRU text:

	WRPKRU will never execute speculatively. Memory accesses
	affected by PKRU register will not execute (even speculatively)
	until all prior executions of WRPKRU have completed execution
	and updated the PKRU register.

Still this will make accessing pmem more expensive from the kernel but
the overhead is minimized and many pmem users access this memory through
user page mappings which are not affected at all.

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
---
 include/linux/highmem.h | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index d6e82e3de027..7f809d8d5a94 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -8,6 +8,7 @@
 #include <linux/mm.h>
 #include <linux/uaccess.h>
 #include <linux/hardirq.h>
+#include <linux/memremap.h>
 
 #include <asm/cacheflush.h>
 
@@ -31,6 +32,20 @@ static inline void invalidate_kernel_vmap_range(void *vaddr, int size)
 
 #include <asm/kmap_types.h>
 
+static inline void enable_access(struct page *page)
+{
+	if (!page_is_access_protected(page))
+		return;
+	dev_access_enable();
+}
+
+static inline void disable_access(struct page *page)
+{
+	if (!page_is_access_protected(page))
+		return;
+	dev_access_disable();
+}
+
 #ifdef CONFIG_HIGHMEM
 extern void *kmap_atomic_high_prot(struct page *page, pgprot_t prot);
 extern void kunmap_atomic_high(void *kvaddr);
@@ -55,6 +70,11 @@ static inline void *kmap(struct page *page)
 	else
 		addr = kmap_high(page);
 	kmap_flush_tlb((unsigned long)addr);
+	/*
+	 * Even non-highmem pages may have additional access protections which
+	 * need to be checked and potentially enabled.
+	 */
+	enable_access(page);
 	return addr;
 }
 
@@ -63,6 +83,11 @@ void kunmap_high(struct page *page);
 static inline void kunmap(struct page *page)
 {
 	might_sleep();
+	/*
+	 * Even non-highmem pages may have additional access protections which
+	 * need to be checked and potentially disabled.
+	 */
+	disable_access(page);
 	if (!PageHighMem(page))
 		return;
 	kunmap_high(page);
@@ -85,6 +110,7 @@ static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot)
 {
 	preempt_disable();
 	pagefault_disable();
+	enable_access(page);
 	if (!PageHighMem(page))
 		return page_address(page);
 	return kmap_atomic_high_prot(page, prot);
@@ -137,6 +163,7 @@ static inline unsigned long totalhigh_pages(void) { return 0UL; }
 static inline void *kmap(struct page *page)
 {
 	might_sleep();
+	enable_access(page);
 	return page_address(page);
 }
 
@@ -146,6 +173,7 @@ static inline void kunmap_high(struct page *page)
 
 static inline void kunmap(struct page *page)
 {
+	disable_access(page);
 #ifdef ARCH_HAS_FLUSH_ON_KUNMAP
 	kunmap_flush_on_unmap(page_address(page));
 #endif
@@ -155,6 +183,7 @@ static inline void *kmap_atomic(struct page *page)
 {
 	preempt_disable();
 	pagefault_disable();
+	enable_access(page);
 	return page_address(page);
 }
 #define kmap_atomic_prot(page, prot)	kmap_atomic(page)
@@ -216,7 +245,8 @@ static inline void kmap_atomic_idx_pop(void)
 #define kunmap_atomic(addr)                                     \
 do {                                                            \
 	BUILD_BUG_ON(__same_type((addr), struct page *));       \
-	kunmap_atomic_high(addr);                                  \
+	disable_access(kmap_to_page(addr));                     \
+	kunmap_atomic_high(addr);                               \
 	pagefault_enable();                                     \
 	preempt_enable();                                       \
 } while (0)
-- 
2.28.0.rc0.12.gb6a658bd00c9


  parent reply	other threads:[~2020-07-17  7:21 UTC|newest]

Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-17  7:20 [PATCH RFC V2 00/17] PKS: Add Protection Keys Supervisor (PKS) support ira.weiny
2020-07-17  7:20 ` [PATCH RFC V2 01/17] x86/pkeys: Create pkeys_internal.h ira.weiny
2020-07-17  7:20 ` [PATCH RFC V2 02/17] x86/fpu: Refactor arch_set_user_pkey_access() for PKS support ira.weiny
2020-07-17  8:54   ` Peter Zijlstra
2020-07-17 20:52     ` Ira Weiny
2020-07-20  9:14       ` Peter Zijlstra
2020-07-17 22:36     ` Dave Hansen
2020-07-20  9:13       ` Peter Zijlstra
2020-07-17  7:20 ` [PATCH RFC V2 03/17] x86/pks: Enable Protection Keys Supervisor (PKS) ira.weiny
2020-07-17  7:20 ` [PATCH RFC V2 04/17] x86/pks: Preserve the PKRS MSR on context switch ira.weiny
2020-07-17  8:31   ` Peter Zijlstra
2020-07-17 21:39     ` Ira Weiny
2020-07-17  8:59   ` Peter Zijlstra
2020-07-17 22:34     ` Ira Weiny
2020-07-20  9:15       ` Peter Zijlstra
2020-07-20 18:35         ` Ira Weiny
2020-07-17  7:20 ` [PATCH RFC V2 05/17] x86/pks: Add PKS kernel API ira.weiny
2020-07-17  7:20 ` [PATCH RFC V2 06/17] x86/pks: Add a debugfs file for allocated PKS keys ira.weiny
2020-07-17  7:20 ` [PATCH RFC V2 07/17] Documentation/pkeys: Update documentation for kernel pkeys ira.weiny
2020-07-17  7:20 ` [PATCH RFC V2 08/17] x86/pks: Add PKS Test code ira.weiny
2020-07-17  7:20 ` [PATCH RFC V2 09/17] memremap: Convert devmap static branch to {inc,dec} ira.weiny
2020-07-17  7:20 ` [PATCH RFC V2 10/17] fs/dax: Remove unused size parameter ira.weiny
2020-07-17  7:20 ` [PATCH RFC V2 11/17] drivers/dax: Expand lock scope to cover the use of addresses ira.weiny
2020-07-17  7:20 ` [PATCH RFC V2 12/17] memremap: Add zone device access protection ira.weiny
2020-07-17  9:10   ` Peter Zijlstra
2020-07-18  5:06     ` Ira Weiny
2020-07-20  9:16       ` Peter Zijlstra
2020-07-17  9:17   ` Peter Zijlstra
2020-07-18  5:51     ` Ira Weiny
2020-07-17  9:20   ` Peter Zijlstra
2020-07-17  7:20 ` ira.weiny [this message]
2020-07-17  9:21   ` [PATCH RFC V2 13/17] kmap: Add stray write protection for device pages Peter Zijlstra
2020-07-19  4:13     ` Ira Weiny
2020-07-20  9:17       ` Peter Zijlstra
2020-07-21 16:31         ` Ira Weiny
2020-07-17  7:20 ` [PATCH RFC V2 14/17] dax: Stray write protection for dax_direct_access() ira.weiny
2020-07-17  9:22   ` Peter Zijlstra
2020-07-19  4:41     ` Ira Weiny
2020-07-17  7:20 ` [PATCH RFC V2 15/17] nvdimm/pmem: Stray write protection for pmem->virt_addr ira.weiny
2020-07-17  7:20 ` [PATCH RFC V2 16/17] [dax|pmem]: Enable stray write protection ira.weiny
2020-07-17  9:25   ` Peter Zijlstra
2020-07-17  7:20 ` [PATCH RFC V2 17/17] x86/entry: Preserve PKRS MSR across exceptions ira.weiny
2020-07-17  9:30   ` Peter Zijlstra
2020-07-21 18:01     ` Ira Weiny
2020-07-21 19:11       ` Peter Zijlstra
2020-07-17  9:34   ` Peter Zijlstra
2020-07-17 10:06   ` Peter Zijlstra
2020-07-22  5:27     ` Ira Weiny
2020-07-22  9:48       ` Peter Zijlstra
2020-07-22 21:24         ` Ira Weiny
2020-07-23 20:08       ` Thomas Gleixner
2020-07-23 20:15         ` Thomas Gleixner
2020-07-24 17:23           ` Ira Weiny
2020-07-24 17:29             ` Andy Lutomirski
2020-07-24 19:43               ` Ira Weiny
2020-07-22 16:21   ` Andy Lutomirski
2020-07-23 16:18     ` Fenghua Yu
2020-07-23 16:23       ` Dave Hansen
2020-07-23 16:52         ` Fenghua Yu
2020-07-23 17:08           ` Andy Lutomirski
2020-07-23 17:30             ` Dave Hansen
2020-07-23 20:23               ` Thomas Gleixner
2020-07-23 20:22             ` Thomas Gleixner
2020-07-23 21:30               ` Andy Lutomirski
2020-07-23 22:14                 ` Thomas Gleixner
2020-07-23 19:53   ` Thomas Gleixner
2020-07-23 22:04     ` Ira Weiny
2020-07-23 23:41       ` Thomas Gleixner
2020-07-24 21:24         ` Thomas Gleixner
2020-07-24 21:31           ` Thomas Gleixner
2020-07-25  0:09           ` Andy Lutomirski
2020-07-27 20:59           ` Ira Weiny
2020-07-24 22:19 ` [PATCH RFC V2 00/17] PKS: Add Protection Keys Supervisor (PKS) support Kees Cook

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200717072056.73134-14-ira.weiny@intel.com \
    --to=ira.weiny@intel.com \
    --cc=akpm@linux-foundation.org \
    --cc=bp@alien8.de \
    --cc=dan.j.williams@intel.com \
    --cc=dave.hansen@linux.intel.com \
    --cc=fenghua.yu@intel.com \
    --cc=linux-doc@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-kselftest@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-nvdimm@lists.01.org \
    --cc=luto@kernel.org \
    --cc=mingo@redhat.com \
    --cc=peterz@infradead.org \
    --cc=tglx@linutronix.de \
    --cc=vishal.l.verma@intel.com \
    --cc=x86@kernel.org \
    --subject='Re: [PATCH RFC V2 13/17] kmap: Add stray write protection for device pages' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).