linux-kernel - [PATCH v2 5/9] riscv: mm: Log potential KASAN shadow alias

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Message-ID: <20241022015913.3524425-6-samuel.holland@sifive.com>
Date: Mon, 21 Oct 2024 18:57:13 -0700
From: Samuel Holland <samuel.holland@...ive.com>
To: Palmer Dabbelt <palmer@...belt.com>,
	linux-riscv@...ts.infradead.org,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Alexander Potapenko <glider@...gle.com>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Vincenzo Frascino <vincenzo.frascino@....com>,
	kasan-dev@...glegroups.com
Cc: llvm@...ts.linux.dev,
	Catalin Marinas <catalin.marinas@....com>,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	Alexandre Ghiti <alexghiti@...osinc.com>,
	Will Deacon <will@...nel.org>,
	Evgenii Stepanov <eugenis@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-arm-kernel@...ts.infradead.org,
	Samuel Holland <samuel.holland@...ive.com>
Subject: [PATCH v2 5/9] riscv: mm: Log potential KASAN shadow alias

When KASAN is enabled, shadow memory is allocated and mapped for all
legitimate kernel addresses, but not for the entire address space. As a
result, the kernel can fault when accessing a shadow address computed
from a bogus pointer. This can be confusing, because the shadow address
computed for (e.g.) NULL looks nothing like a NULL pointer. To assist
debugging, if the faulting address might be the result of a KASAN shadow
memory address computation, report the range of original memory
addresses that would map to the faulting address.

Signed-off-by: Samuel Holland <samuel.holland@...ive.com>
---

Changes in v2:
 - New patch for v2

 arch/riscv/mm/fault.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
index a9f2b4af8f3f..dae1131221b7 100644
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -8,6 +8,7 @@
 
 
 #include <linux/mm.h>
+#include <linux/kasan.h>
 #include <linux/kernel.h>
 #include <linux/interrupt.h>
 #include <linux/perf_event.h>
@@ -30,6 +31,8 @@ static void die_kernel_fault(const char *msg, unsigned long addr,
 	pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n", msg,
 		addr);
 
+	kasan_non_canonical_hook(addr);
+
 	bust_spinlocks(0);
 	die(regs, "Oops");
 	make_task_dead(SIGKILL);
-- 
2.45.1