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Date: Fri, 21 Dec 2018 20:14:15 +0200
From: Igor Stoppa <igor.stoppa@...il.com>
To: Andy Lutomirski <luto@...capital.net>,
	Matthew Wilcox <willy@...radead.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Thiago Jung Bauermann <bauerman@...ux.ibm.com>
Cc: igor.stoppa@...wei.com,
	Nadav Amit <nadav.amit@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Ahmed Soliman <ahmedsoliman@...a.vt.edu>,
	linux-integrity@...r.kernel.org,
	kernel-hardening@...ts.openwall.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 04/12] __wr_after_init: debug writes

After each write operation, confirm that it was successful, otherwise
generate a warning.

Signed-off-by: Igor Stoppa <igor.stoppa@...wei.com>

CC: Andy Lutomirski <luto@...capital.net>
CC: Nadav Amit <nadav.amit@...il.com>
CC: Matthew Wilcox <willy@...radead.org>
CC: Peter Zijlstra <peterz@...radead.org>
CC: Kees Cook <keescook@...omium.org>
CC: Dave Hansen <dave.hansen@...ux.intel.com>
CC: Mimi Zohar <zohar@...ux.vnet.ibm.com>
CC: Thiago Jung Bauermann <bauerman@...ux.ibm.com>
CC: Ahmed Soliman <ahmedsoliman@...a.vt.edu>
CC: linux-integrity@...r.kernel.org
CC: kernel-hardening@...ts.openwall.com
CC: linux-mm@...ck.org
CC: linux-kernel@...r.kernel.org
---
 mm/Kconfig.debug | 8 ++++++++
 mm/prmem.c       | 6 ++++++
 2 files changed, 14 insertions(+)

diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index 9a7b8b049d04..b10305cfac3c 100644
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -94,3 +94,11 @@ config DEBUG_RODATA_TEST
     depends on STRICT_KERNEL_RWX
     ---help---
       This option enables a testcase for the setting rodata read-only.
+
+config DEBUG_PRMEM
+    bool "Verify each write rare operation."
+    depends on PRMEM
+    default n
+    help
+      After any write rare operation, compares the data written with the
+      value provided by the caller.
diff --git a/mm/prmem.c b/mm/prmem.c
index e1c1be3a1171..51f6776e2515 100644
--- a/mm/prmem.c
+++ b/mm/prmem.c
@@ -61,6 +61,9 @@ void *wr_memcpy(void *p, const void *q, __kernel_size_t size)
 	__wr_enable(&wr_state);
 	__wr_memcpy(wr_poking_addr, q, size);
 	__wr_disable(&wr_state);
+#ifdef CONFIG_DEBUG_PRMEM
+	VM_WARN_ONCE(memcmp(p, q, size), "Failed %s()", __func__);
+#endif
 	local_irq_enable();
 	return p;
 }
@@ -92,6 +95,9 @@ void *wr_memset(void *p, int c, __kernel_size_t len)
 	__wr_enable(&wr_state);
 	__wr_memset(wr_poking_addr, c, len);
 	__wr_disable(&wr_state);
+#ifdef CONFIG_DEBUG_PRMEM
+	VM_WARN_ONCE(memtst(p, c, len), "Failed %s()", __func__);
+#endif
 	local_irq_enable();
 	return p;
 }
-- 
2.19.1

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