We found this issue in an legacy out-of-tree kernel module
which didn't properly access user space pointer by get/put_user().
Such an illegal access loops in the page fault handler.
To resolve this, let it die here.
Signed-off-by: Eric Lin <[email protected]>
Cc: Alan Kao <[email protected]>
Reviewed-by: Pekka Enberg <[email protected]>
---
arch/riscv/mm/fault.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
index 0d5f06d6e3c7..33d284188f9a 100644
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -243,6 +243,11 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
if (user_mode(regs))
flags |= FAULT_FLAG_USER;
+ if (!user_mode(regs) && addr < TASK_SIZE &&
+ unlikely(!(regs->status & SR_SUM)))
+ die_kernel_fault("access to user memory without uaccess routines",
+ addr, regs);
+
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
if (cause == EXC_STORE_PAGE_FAULT)
--
2.17.0