linux-kernel - [PATCH] RISC-V: Acquire mmap lock before invoking walk_page

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Date:   Wed, 17 Jun 2020 13:37:32 -0700
From:   Atish Patra <atish.patra@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Atish Patra <atish.patra@....com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        linux-riscv@...ts.infradead.org,
        Michel Lespinasse <walken@...gle.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Zong Li <zong.li@...ive.com>
Subject: [PATCH] RISC-V: Acquire mmap lock before invoking walk_page_range

As per walk_page_range documentation, mmap lock should be acquired by the
caller before invoking walk_page_range. mmap_assert_locked gets triggered
without that. The details can be found here.

http://lists.infradead.org/pipermail/linux-riscv/2020-June/010335.html

Fixes: 395a21ff859c(riscv: add ARCH_HAS_SET_DIRECT_MAP support)
Signed-off-by: Atish Patra <atish.patra@....com>
---
 arch/riscv/mm/pageattr.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c
index ec2c70f84994..289a9a5ea5b5 100644
--- a/arch/riscv/mm/pageattr.c
+++ b/arch/riscv/mm/pageattr.c
@@ -151,6 +151,7 @@ int set_memory_nx(unsigned long addr, int numpages)
 
 int set_direct_map_invalid_noflush(struct page *page)
 {
+	int ret;
 	unsigned long start = (unsigned long)page_address(page);
 	unsigned long end = start + PAGE_SIZE;
 	struct pageattr_masks masks = {
@@ -158,11 +159,16 @@ int set_direct_map_invalid_noflush(struct page *page)
 		.clear_mask = __pgprot(_PAGE_PRESENT)
 	};
 
-	return walk_page_range(&init_mm, start, end, &pageattr_ops, &masks);
+	mmap_read_lock(&init_mm);
+	ret = walk_page_range(&init_mm, start, end, &pageattr_ops, &masks);
+	mmap_read_unlock(&init_mm);
+
+	return ret;
 }
 
 int set_direct_map_default_noflush(struct page *page)
 {
+	int ret;
 	unsigned long start = (unsigned long)page_address(page);
 	unsigned long end = start + PAGE_SIZE;
 	struct pageattr_masks masks = {
@@ -170,7 +176,11 @@ int set_direct_map_default_noflush(struct page *page)
 		.clear_mask = __pgprot(0)
 	};
 
-	return walk_page_range(&init_mm, start, end, &pageattr_ops, &masks);
+	mmap_read_lock(&init_mm);
+	ret = walk_page_range(&init_mm, start, end, &pageattr_ops, &masks);
+	mmap_read_unlock(&init_mm);
+
+	return ret;
 }
 
 void __kernel_map_pages(struct page *page, int numpages, int enable)
-- 
2.26.2