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Date:   Tue, 10 Nov 2020 23:10:37 +0100
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Subject: [PATCH v9 40/44] kasan, arm64: print report from tag fault handler
From:   Andrey Konovalov <andreyknvl@google.com>
To:     Catalin Marinas <catalin.marinas@arm.com>
Cc:     Will Deacon <will.deacon@arm.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Marco Elver <elver@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        Branislav Rankov <Branislav.Rankov@arm.com>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        kasan-dev@googlegroups.com, linux-arm-kernel@lists.infradead.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Andrey Konovalov <andreyknvl@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Add error reporting for hardware tag-based KASAN. When CONFIG_KASAN_HW_TAGS
is enabled, print KASAN report from the arm64 tag fault handler.

SAS bits aren't set in ESR for all faults reported in EL1, so it's
impossible to find out the size of the access the caused the fault.
Adapt KASAN reporting code to handle this case.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Co-developed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
---
Change-Id: I3780fe7db6e075dff2937d3d8508f55c9322b095
---
 arch/arm64/mm/fault.c | 14 ++++++++++++++
 mm/kasan/report.c     | 11 ++++++++---
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index fbceb14d93b1..7370e822e588 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -14,6 +14,7 @@
 #include <linux/mm.h>
 #include <linux/hardirq.h>
 #include <linux/init.h>
+#include <linux/kasan.h>
 #include <linux/kprobes.h>
 #include <linux/uaccess.h>
 #include <linux/page-flags.h>
@@ -297,10 +298,23 @@ static void die_kernel_fault(const char *msg, unsigned long addr,
 	do_exit(SIGKILL);
 }
 
+#ifdef CONFIG_KASAN_HW_TAGS
 static void report_tag_fault(unsigned long addr, unsigned int esr,
 			     struct pt_regs *regs)
 {
+	bool is_write  = ((esr & ESR_ELx_WNR) >> ESR_ELx_WNR_SHIFT) != 0;
+
+	/*
+	 * SAS bits aren't set for all faults reported in EL1, so we can't
+	 * find out access size.
+	 */
+	kasan_report(addr, 0, is_write, regs->pc);
 }
+#else
+/* Tag faults aren't enabled without CONFIG_KASAN_HW_TAGS. */
+static inline void report_tag_fault(unsigned long addr, unsigned int esr,
+				    struct pt_regs *regs) { }
+#endif
 
 static void do_tag_recovery(unsigned long addr, unsigned int esr,
 			   struct pt_regs *regs)
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 8afc1a6ab202..ce06005d4052 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -62,9 +62,14 @@ static void print_error_description(struct kasan_access_info *info)
 {
 	pr_err("BUG: KASAN: %s in %pS\n",
 		get_bug_type(info), (void *)info->ip);
-	pr_err("%s of size %zu at addr %px by task %s/%d\n",
-		info->is_write ? "Write" : "Read", info->access_size,
-		info->access_addr, current->comm, task_pid_nr(current));
+	if (info->access_size)
+		pr_err("%s of size %zu at addr %px by task %s/%d\n",
+			info->is_write ? "Write" : "Read", info->access_size,
+			info->access_addr, current->comm, task_pid_nr(current));
+	else
+		pr_err("%s at addr %px by task %s/%d\n",
+			info->is_write ? "Write" : "Read",
+			info->access_addr, current->comm, task_pid_nr(current));
 }
 
 static DEFINE_SPINLOCK(report_lock);
-- 
2.29.2.222.g5d2a92d10f8-goog