[PATCH] riscv/mm: Prevent kernel module access user-space memory without uaccess routines

[Eric Lin]

In the page fault handler, an access to user-space memory
without get/put_user() or copy_from/to_user() routines is
not resolved properly. Like arm and other architectures,
we need to let it die earlier in page fault handler.

Signed-off-by: Eric Lin <tesheng@xxxxxxxxxxxxx>
Cc: Alan Kao <alankao@xxxxxxxxxxxxx>
---
 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 3c8b9e433c67..a452cfa266a2 100644
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -232,6 +232,9 @@ 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(regs, "Accessing user space memory without uaccess routines\n");
+
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
 
 	if (cause == EXC_STORE_PAGE_FAULT)
-- 
2.17.0