pve-edge-kernel/patches/kernel/0180-x86-mm-Remove-hard-coded-ASID-limit-checks.patch

From f847420cd768a0b95c3159ab822c30c909f0e5ee Mon Sep 17 00:00:00 2001
From: Dave Hansen <[email protected]>
Date: Mon, 4 Dec 2017 15:07:55 +0100
Subject: [PATCH 180/242] x86/mm: Remove hard-coded ASID limit checks
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CVE-2017-5754

First, it's nice to remove the magic numbers.

Second, PAGE_TABLE_ISOLATION is going to consume half of the available ASID
space.  The space is currently unused, but add a comment to spell out this
new restriction.

Signed-off-by: Dave Hansen <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: David Laight <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: Eduardo Valentin <[email protected]>
Cc: Greg KH <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Ingo Molnar <[email protected]>
(cherry picked from commit cb0a9144a744e55207e24dcef812f05cd15a499a)
Signed-off-by: Andy Whitcroft <[email protected]>
Signed-off-by: Kleber Sacilotto de Souza <[email protected]>
(cherry picked from commit fd5d001ae73ccd382d4270f53e27dcf61c4e4749)
Signed-off-by: Fabian Grünbichler <[email protected]>
---
 arch/x86/include/asm/tlbflush.h | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 3a421b164868..c1c10db4156c 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -68,6 +68,22 @@ static inline u64 inc_mm_tlb_gen(struct mm_struct *mm)
 	return atomic64_inc_return(&mm->context.tlb_gen);
 }
 
+/* There are 12 bits of space for ASIDS in CR3 */
+#define CR3_HW_ASID_BITS		12
+/*
+ * When enabled, PAGE_TABLE_ISOLATION consumes a single bit for
+ * user/kernel switches
+ */
+#define PTI_CONSUMED_ASID_BITS		0
+
+#define CR3_AVAIL_ASID_BITS (CR3_HW_ASID_BITS - PTI_CONSUMED_ASID_BITS)
+/*
+ * ASIDs are zero-based: 0->MAX_AVAIL_ASID are valid.  -1 below to account
+ * for them being zero-based.  Another -1 is because ASID 0 is reserved for
+ * use by non-PCID-aware users.
+ */
+#define MAX_ASID_AVAILABLE ((1 << CR3_AVAIL_ASID_BITS) - 2)
+
 /*
  * If PCID is on, ASID-aware code paths put the ASID+1 into the PCID bits.
  * This serves two purposes.  It prevents a nasty situation in which
@@ -80,7 +96,7 @@ struct pgd_t;
 static inline unsigned long build_cr3(pgd_t *pgd, u16 asid)
 {
 	if (static_cpu_has(X86_FEATURE_PCID)) {
-		VM_WARN_ON_ONCE(asid > 4094);
+		VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
 		return __sme_pa(pgd) | (asid + 1);
 	} else {
 		VM_WARN_ON_ONCE(asid != 0);
@@ -90,7 +106,7 @@ static inline unsigned long build_cr3(pgd_t *pgd, u16 asid)
 
 static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid)
 {
-	VM_WARN_ON_ONCE(asid > 4094);
+	VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
 	return __sme_pa(pgd) | (asid + 1) | CR3_NOFLUSH;
 }
 
-- 
2.14.2