linux-kernel - [PATCH 5.7 233/244] RISC-V: Acquire mmap lock before invoking walk_page

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Date:   Mon, 20 Jul 2020 17:38:24 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Atish Patra <atish.patra@....com>,
        Michel Lespinasse <walken@...gle.com>,
        Zong Li <zong.li@...ive.com>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>
Subject: [PATCH 5.7 233/244] RISC-V: Acquire mmap lock before invoking walk_page_range

From: Atish Patra <atish.patra@....com>

commit 0e2c09011d4de4161f615ff860a605a9186cf62a upstream.

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>
Reviewed-by: Michel Lespinasse <walken@...gle.com>
Reviewed-by: Zong Li <zong.li@...ive.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/riscv/mm/pageattr.c |   14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

--- a/arch/riscv/mm/pageattr.c
+++ b/arch/riscv/mm/pageattr.c
@@ -151,6 +151,7 @@ int set_memory_nx(unsigned long addr, in
 
 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(struc
 		.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(struc
 		.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)