linux-kernel - [PATCH 3.16 125/148] xtensa: fix TLB sanity checker

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Date:   Sat, 08 Feb 2020 18:21:04 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Max Filippov" <jcmvbkbc@...il.com>
Subject: [PATCH 3.16 125/148] xtensa: fix TLB sanity checker

3.16.82-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Max Filippov <jcmvbkbc@...il.com>

commit 36de10c4788efc6efe6ff9aa10d38cb7eea4c818 upstream.

Virtual and translated addresses retrieved by the xtensa TLB sanity
checker must be consistent, i.e. correspond to the same state of the
checked TLB entry. KASAN shadow memory is mapped dynamically using
auto-refill TLB entries and thus may change TLB state between the
virtual and translated address retrieval, resulting in false TLB
insanity report.
Move read_xtlb_translation close to read_xtlb_virtual to make sure that
read values are consistent.

Fixes: a99e07ee5e88 ("xtensa: check TLB sanity on return to userspace")
Signed-off-by: Max Filippov <jcmvbkbc@...il.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/xtensa/mm/tlb.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/xtensa/mm/tlb.c
+++ b/arch/xtensa/mm/tlb.c
@@ -218,6 +218,8 @@ static int check_tlb_entry(unsigned w, u
 	unsigned tlbidx = w | (e << PAGE_SHIFT);
 	unsigned r0 = dtlb ?
 		read_dtlb_virtual(tlbidx) : read_itlb_virtual(tlbidx);
+	unsigned r1 = dtlb ?
+		read_dtlb_translation(tlbidx) : read_itlb_translation(tlbidx);
 	unsigned vpn = (r0 & PAGE_MASK) | (e << PAGE_SHIFT);
 	unsigned pte = get_pte_for_vaddr(vpn);
 	unsigned mm_asid = (get_rasid_register() >> 8) & ASID_MASK;
@@ -233,8 +235,6 @@ static int check_tlb_entry(unsigned w, u
 	}
 
 	if (tlb_asid == mm_asid) {
-		unsigned r1 = dtlb ? read_dtlb_translation(tlbidx) :
-			read_itlb_translation(tlbidx);
 		if ((pte ^ r1) & PAGE_MASK) {
 			pr_err("%cTLB: way: %u, entry: %u, mapping: %08x->%08x, PTE: %08x\n",
 					dtlb ? 'D' : 'I', w, e, r0, r1, pte);