[PATCH v2 34/37] kasan, arm64: print report from tag fault handler

[Andrey Konovalov]

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 at google.com>
Co-developed-by: Vincenzo Frascino <vincenzo.frascino at arm.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino at arm.com>
---
Change-Id: I3780fe7db6e075dff2937d3d8508f55c9322b095
---
 arch/arm64/mm/fault.c | 19 +++++++++++++------
 mm/kasan/report.c     | 11 ++++++++---
 2 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index cdc23662691c..ac79819317f2 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>
@@ -295,17 +296,23 @@ 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;
+	bool is_write  = ((esr & ESR_ELx_WNR) >> ESR_ELx_WNR_SHIFT) != 0;
 
-	pr_alert("Memory Tagging Extension Fault in %pS\n", (void *)regs->pc);
-	pr_alert("  %s at address %lx\n", is_write ? "Write" : "Read", addr);
-	pr_alert("  Pointer tag: [%02x], memory tag: [%02x]\n",
-			mte_get_ptr_tag(addr),
-			mte_get_mem_tag((void *)addr));
+	/*
+	 * 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_kernel_fault(unsigned long addr, unsigned int esr,
 			      struct pt_regs *regs)
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index c904edab33b8..34ef81736d73 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -65,9 +65,14 @@ 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);
-- 
2.28.0.618.gf4bc123cb7-goog