linux-kernel - [PATCH 3.12 110/127] sparc: Don't leak context bits into thread->fault

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Date:   Fri, 25 Nov 2016 09:30:23 +0100
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 110/127] sparc: Don't leak context bits into thread->fault_address

From: "David S. Miller" <davem@...emloft.net>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

[ Upstream commit 4f6deb8cbab532a8d7250bc09234c1795ecb5e2c ]

On pre-Niagara systems, we fetch the fault address on data TLB
exceptions from the TLB_TAG_ACCESS register.  But this register also
contains the context ID assosciated with the fault in the low 13 bits
of the register value.

This propagates into current_thread_info()->fault_address and can
cause trouble later on.

So clear the low 13-bits out of the TLB_TAG_ACCESS value in the cases
where it matters.

Reported-by: Mikulas Patocka <mpatocka@...hat.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 arch/sparc/kernel/dtlb_prot.S |  4 ++--
 arch/sparc/kernel/ktlb.S      | 12 ++++++++++++
 arch/sparc/kernel/tsb.S       | 12 ++++++++++--
 3 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/arch/sparc/kernel/dtlb_prot.S b/arch/sparc/kernel/dtlb_prot.S
index d668ca149e64..4087a62f96b0 100644
--- a/arch/sparc/kernel/dtlb_prot.S
+++ b/arch/sparc/kernel/dtlb_prot.S
@@ -25,13 +25,13 @@
 
 /* PROT ** ICACHE line 2: More real fault processing */
 	ldxa		[%g4] ASI_DMMU, %g5		! Put tagaccess in %g5
+	srlx		%g5, PAGE_SHIFT, %g5
+	sllx		%g5, PAGE_SHIFT, %g5		! Clear context ID bits
 	bgu,pn		%xcc, winfix_trampoline		! Yes, perform winfixup
 	 mov		FAULT_CODE_DTLB | FAULT_CODE_WRITE, %g4
 	ba,pt		%xcc, sparc64_realfault_common	! Nope, normal fault
 	 nop
 	nop
-	nop
-	nop
 
 /* PROT ** ICACHE line 3: Unused...	*/
 	nop
diff --git a/arch/sparc/kernel/ktlb.S b/arch/sparc/kernel/ktlb.S
index ef0d8e9e1210..f22bec0db645 100644
--- a/arch/sparc/kernel/ktlb.S
+++ b/arch/sparc/kernel/ktlb.S
@@ -20,6 +20,10 @@ kvmap_itlb:
 	mov		TLB_TAG_ACCESS, %g4
 	ldxa		[%g4] ASI_IMMU, %g4
 
+	/* The kernel executes in context zero, therefore we do not
+	 * need to clear the context ID bits out of %g4 here.
+	 */
+
 	/* sun4v_itlb_miss branches here with the missing virtual
 	 * address already loaded into %g4
 	 */
@@ -128,6 +132,10 @@ kvmap_dtlb:
 	mov		TLB_TAG_ACCESS, %g4
 	ldxa		[%g4] ASI_DMMU, %g4
 
+	/* The kernel executes in context zero, therefore we do not
+	 * need to clear the context ID bits out of %g4 here.
+	 */
+
 	/* sun4v_dtlb_miss branches here with the missing virtual
 	 * address already loaded into %g4
 	 */
@@ -251,6 +259,10 @@ kvmap_dtlb_longpath:
 	nop
 	.previous
 
+	/* The kernel executes in context zero, therefore we do not
+	 * need to clear the context ID bits out of %g5 here.
+	 */
+
 	be,pt	%xcc, sparc64_realfault_common
 	 mov	FAULT_CODE_DTLB, %g4
 	ba,pt	%xcc, winfix_trampoline
diff --git a/arch/sparc/kernel/tsb.S b/arch/sparc/kernel/tsb.S
index be98685c14c6..d568c8207af7 100644
--- a/arch/sparc/kernel/tsb.S
+++ b/arch/sparc/kernel/tsb.S
@@ -29,13 +29,17 @@
 	 */
 tsb_miss_dtlb:
 	mov		TLB_TAG_ACCESS, %g4
+	ldxa		[%g4] ASI_DMMU, %g4
+	srlx		%g4, PAGE_SHIFT, %g4
 	ba,pt		%xcc, tsb_miss_page_table_walk
-	 ldxa		[%g4] ASI_DMMU, %g4
+	 sllx		%g4, PAGE_SHIFT, %g4
 
 tsb_miss_itlb:
 	mov		TLB_TAG_ACCESS, %g4
+	ldxa		[%g4] ASI_IMMU, %g4
+	srlx		%g4, PAGE_SHIFT, %g4
 	ba,pt		%xcc, tsb_miss_page_table_walk
-	 ldxa		[%g4] ASI_IMMU, %g4
+	 sllx		%g4, PAGE_SHIFT, %g4
 
 	/* At this point we have:
 	 * %g1 --	PAGE_SIZE TSB entry address
@@ -284,6 +288,10 @@ tsb_do_dtlb_fault:
 	nop
 	.previous
 
+	/* Clear context ID bits.  */
+	srlx		%g5, PAGE_SHIFT, %g5
+	sllx		%g5, PAGE_SHIFT, %g5
+
 	be,pt	%xcc, sparc64_realfault_common
 	 mov	FAULT_CODE_DTLB, %g4
 	ba,pt	%xcc, winfix_trampoline
-- 
2.10.2