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

From: Eric Lin <tesheng@andestech.com>
To: <linux-kernel@vger.kernel.org>, <linux-riscv@lists.infradead.org>,
	<walken@google.com>, <daniel.m.jordan@oracle.com>,
	<peterx@redhat.com>, <akpm@linux-foundation.org>,
	<penberg@kernel.org>, <aou@eecs.berkeley.edu>,
	<palmer@dabbelt.com>, <paul.walmsley@sifive.com>
Cc: Eric Lin <tesheng@andestech.com>,
	dslin1010@gmail.com, Alan Kao <alankao@andestech.com>
Subject: [PATCH] riscv/mm: Prevent kernel module access user-space memory without uaccess routines
Date: Mon, 30 Nov 2020 13:30:37 +0800	[thread overview]
Message-ID: <20201130053037.27006-1-tesheng@andestech.com> (raw)

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@andestech.com>
Cc: Alan Kao <alankao@andestech.com>
---
 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


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