linux-kernel - [PATCH v1 1/6] powerpc/mm: Fix reporting of kernel execute faults on the 8xx

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Message-Id: <ab8fcb458e1a6ad86382767b3ce7f7cc0d5b7121.1541568127.git.christophe.leroy@c-s.fr>
Date:   Wed,  7 Nov 2018 16:56:27 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>, ruscur@...sell.cc
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v1 1/6] powerpc/mm: Fix reporting of kernel execute faults
 on the 8xx

On the 8xx, no-execute is set via PPP bits in the PTE. Therefore
a no-exec fault generates DSISR_PROTFAULT error bits,
not DSISR_NOEXEC_OR_G.

This patch adds DSISR_PROTFAULT in the test mask.

Fixes: d3ca587404b3 ("powerpc/mm: Fix reporting of kernel execute faults")
Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
 arch/powerpc/mm/fault.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 1697e903bbf2..50e5c790d11e 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -226,7 +226,9 @@ static int mm_fault_error(struct pt_regs *regs, unsigned long addr,
 static bool bad_kernel_fault(bool is_exec, unsigned long error_code,
 			     unsigned long address)
 {
-	if (is_exec && (error_code & (DSISR_NOEXEC_OR_G | DSISR_KEYFAULT))) {
+	/* NX faults set DSISR_PROTFAULT on the 8xx, DSISR_NOEXEC_OR_G on others */
+	if (is_exec && (error_code & (DSISR_NOEXEC_OR_G | DSISR_KEYFAULT |
+				      DSISR_PROTFAULT))) {
 		printk_ratelimited(KERN_CRIT "kernel tried to execute"
 				   " exec-protected page (%lx) -"
 				   "exploit attempt? (uid: %d)\n",
-- 
2.13.3