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

Samuel Holland
2024-10-22T03:15:46Z

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@sifive.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