linux-kernel - [PATCH 1/2] kfence: add function to mask address bits

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Message-Id: <20210514092139.3225509-2-svens@linux.ibm.com>
Date:   Fri, 14 May 2021 11:21:38 +0200
From:   Sven Schnelle <svens@...ux.ibm.com>
To:     Marco Elver <elver@...gle.com>
Cc:     linux-kernel@...r.kernel.org, Sven Schnelle <svens@...ux.ibm.com>
Subject: [PATCH 1/2] kfence: add function to mask address bits

s390 only reports the page address during a translation fault.
To make the kfence unit tests pass, add a function that might
be implemented by architectures to mask out address bits.

Signed-off-by: Sven Schnelle <svens@...ux.ibm.com>
---
 include/linux/kfence.h  | 1 +
 mm/kfence/core.c        | 5 +++++
 mm/kfence/kfence_test.c | 6 +++++-
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/linux/kfence.h b/include/linux/kfence.h
index a70d1ea03532..2e15f4c4ee95 100644
--- a/include/linux/kfence.h
+++ b/include/linux/kfence.h
@@ -199,6 +199,7 @@ static __always_inline __must_check bool kfence_free(void *addr)
  * present, so that the kernel can proceed.
  */
 bool __must_check kfence_handle_page_fault(unsigned long addr, bool is_write, struct pt_regs *regs);
+unsigned long kfence_arch_mask_addr(unsigned long addr);
 
 #else /* CONFIG_KFENCE */
 
diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index e18fbbd5d9b4..bc15e3cb71d5 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -50,6 +50,11 @@ static unsigned long kfence_sample_interval __read_mostly = CONFIG_KFENCE_SAMPLE
 #endif
 #define MODULE_PARAM_PREFIX "kfence."
 
+unsigned long __weak kfence_arch_mask_addr(unsigned long addr)
+{
+	return addr;
+}
+
 static int param_set_sample_interval(const char *val, const struct kernel_param *kp)
 {
 	unsigned long num;
diff --git a/mm/kfence/kfence_test.c b/mm/kfence/kfence_test.c
index 4acf4251ee04..9ec572991014 100644
--- a/mm/kfence/kfence_test.c
+++ b/mm/kfence/kfence_test.c
@@ -82,6 +82,7 @@ static const char *get_access_type(const struct expect_report *r)
 /* Check observed report matches information in @r. */
 static bool report_matches(const struct expect_report *r)
 {
+	unsigned long addr = (unsigned long)r->addr;
 	bool ret = false;
 	unsigned long flags;
 	typeof(observed.lines) expect;
@@ -131,22 +132,25 @@ static bool report_matches(const struct expect_report *r)
 	switch (r->type) {
 	case KFENCE_ERROR_OOB:
 		cur += scnprintf(cur, end - cur, "Out-of-bounds %s at", get_access_type(r));
+		addr = kfence_arch_mask_addr(addr);
 		break;
 	case KFENCE_ERROR_UAF:
 		cur += scnprintf(cur, end - cur, "Use-after-free %s at", get_access_type(r));
+		addr = kfence_arch_mask_addr(addr);
 		break;
 	case KFENCE_ERROR_CORRUPTION:
 		cur += scnprintf(cur, end - cur, "Corrupted memory at");
 		break;
 	case KFENCE_ERROR_INVALID:
 		cur += scnprintf(cur, end - cur, "Invalid %s at", get_access_type(r));
+		addr = kfence_arch_mask_addr(addr);
 		break;
 	case KFENCE_ERROR_INVALID_FREE:
 		cur += scnprintf(cur, end - cur, "Invalid free of");
 		break;
 	}
 
-	cur += scnprintf(cur, end - cur, " 0x%p", (void *)r->addr);
+	cur += scnprintf(cur, end - cur, " 0x%p", (void *)addr);
 
 	spin_lock_irqsave(&observed.lock, flags);
 	if (!report_available())
-- 
2.25.1