[PATCH] riscv: pageattr: Fixup synchronization problem between init_mm and active_mm

From: guoren@kernel.org
To: guoren@kernel.org, palmer@rivosinc.com, paul.walmsley@sifive.co,
	zong.li@sifive.com, atishp@atishpatra.org, alex@ghiti.fr,
	jszhang@kernel.org, bjorn@kernel.org
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-riscv@lists.infradead.org,
	Guo Ren <guoren@linux.alibaba.com>
Subject: [PATCH] riscv: pageattr: Fixup synchronization problem between init_mm and active_mm
Date: Thu, 29 Jun 2023 04:20:32 -0400	[thread overview]
Message-ID: <20230629082032.3481237-1-guoren@kernel.org> (raw)

From: Guo Ren <guoren@linux.alibaba.com>

The machine_kexec() uses set_memory_x to add the executable attribute to the
page table entry of control_code_buffer. It only modifies the init_mm but not
the current->active_mm. The current kexec process won't use init_mm directly,
and it depends on minor_pagefault, which is removed by commit 7d3332be011e4
("riscv: mm: Pre-allocate PGD entries for vmalloc/modules area") of 64BIT. So,
when it met pud mapping on an MMU_SV39 machine, it caused the following:

 kexec_core: Starting new kernel
 Will call new kernel at 00300000 from hart id 0
 FDT image at 747c7000
 Bye...
 Unable to handle kernel paging request at virtual address ffffffda23b0d000
 Oops [#1]
 Modules linked in:
 CPU: 0 PID: 53 Comm: uinit Not tainted 6.4.0-rc6 #15
 Hardware name: Sophgo Mango (DT)
 epc : 0xffffffda23b0d000
  ra : machine_kexec+0xa6/0xb0
 epc : ffffffda23b0d000 ra : ffffffff80008272 sp : ffffffc80c173d10
  gp : ffffffff8150e1e0 tp : ffffffd9073d2c40 t0 : 0000000000000000
  t1 : 0000000000000042 t2 : 6567616d69205444 s0 : ffffffc80c173d50
  s1 : ffffffd9076c4800 a0 : ffffffd9076c4800 a1 : 0000000000300000
  a2 : 00000000747c7000 a3 : 0000000000000000 a4 : ffffffd800000000
  a5 : 0000000000000000 a6 : ffffffd903619c40 a7 : ffffffffffffffff
  s2 : ffffffda23b0d000 s3 : 0000000000300000 s4 : 00000000747c7000
  s5 : 0000000000000000 s6 : 0000000000000000 s7 : 0000000000000000
  s8 : 0000000000000000 s9 : 0000000000000000 s10: 0000000000000000
  s11: 0000003f940001a0 t3 : ffffffff815351af t4 : ffffffff815351af
  t5 : ffffffff815351b0 t6 : ffffffc80c173b50
 status: 0000000200000100 badaddr: ffffffda23b0d000 cause: 000000000000000c

Yes, Using set_memory_x API after boot has the limitation, and at least we
should synchronize the current->active_mm to fix the problem.

Fixes: d3ab332a5021 ("riscv: add ARCH_HAS_SET_MEMORY support")
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
---
 arch/riscv/mm/pageattr.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c
index ea3d61de065b..23d169c4ee81 100644
--- a/arch/riscv/mm/pageattr.c
+++ b/arch/riscv/mm/pageattr.c
@@ -123,6 +123,13 @@ static int __set_memory(unsigned long addr, int numpages, pgprot_t set_mask,
 				     &masks);
 	mmap_write_unlock(&init_mm);
 
+	if (current->active_mm != &init_mm) {
+		mmap_write_lock(current->active_mm);
+		ret =  walk_page_range_novma(current->active_mm, start, end,
+					     &pageattr_ops, NULL, &masks);
+		mmap_write_unlock(current->active_mm);
+	}
+
 	flush_tlb_kernel_range(start, end);
 
 	return ret;
-- 
2.36.1


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