linux-kernel - [PATCH] openrisc: Fix pagewalk usage in arch_dma_{clear, set}

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Message-Id: <20221008052422.29695-1-shorne@gmail.com>
Date:   Sat,  8 Oct 2022 06:24:21 +0100
From:   Stafford Horne <shorne@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     openrisc@...ts.librecores.org, Jann Horn <jannh@...gle.com>,
        Stafford Horne <shorne@...il.com>,
        Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Steven Price <steven.price@....com>
Subject: [PATCH] openrisc: Fix pagewalk usage in arch_dma_{clear, set}_uncached

From: Jann Horn <jannh@...gle.com>

Since commit 8782fb61cc848 ("mm: pagewalk: Fix race between unmap and page
walker"), walk_page_range() on kernel ranges won't work anymore,
walk_page_range_novma() must be used instead.

Note: I don't have an openrisc development setup, so this is completely
untested.

Fixes: 8782fb61cc848 ("mm: pagewalk: Fix race between unmap and page walker")
Signed-off-by: Jann Horn <jannh@...gle.com>
Signed-off-by: Stafford Horne <shorne@...il.com>
---
Since v1:
 - Repost to include LKML.
 - Added my SOB
 - I tested this by booking this on the qemu virt platform and it works fine.

 arch/openrisc/kernel/dma.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/openrisc/kernel/dma.c b/arch/openrisc/kernel/dma.c
index a82b2caaa560..b3edbb33b621 100644
--- a/arch/openrisc/kernel/dma.c
+++ b/arch/openrisc/kernel/dma.c
@@ -74,10 +74,10 @@ void *arch_dma_set_uncached(void *cpu_addr, size_t size)
 	 * We need to iterate through the pages, clearing the dcache for
 	 * them and setting the cache-inhibit bit.
 	 */
-	mmap_read_lock(&init_mm);
-	error = walk_page_range(&init_mm, va, va + size, &set_nocache_walk_ops,
-			NULL);
-	mmap_read_unlock(&init_mm);
+	mmap_write_lock(&init_mm);
+	error = walk_page_range_novma(&init_mm, va, va + size,
+			&set_nocache_walk_ops, NULL, NULL);
+	mmap_write_unlock(&init_mm);
 
 	if (error)
 		return ERR_PTR(error);
@@ -88,11 +88,11 @@ void arch_dma_clear_uncached(void *cpu_addr, size_t size)
 {
 	unsigned long va = (unsigned long)cpu_addr;
 
-	mmap_read_lock(&init_mm);
+	mmap_write_lock(&init_mm);
 	/* walk_page_range shouldn't be able to fail here */
-	WARN_ON(walk_page_range(&init_mm, va, va + size,
-			&clear_nocache_walk_ops, NULL));
-	mmap_read_unlock(&init_mm);
+	WARN_ON(walk_page_range_novma(&init_mm, va, va + size,
+			&clear_nocache_walk_ops, NULL, NULL));
+	mmap_write_unlock(&init_mm);
 }
 
 void arch_sync_dma_for_device(phys_addr_t addr, size_t size,
-- 
2.37.2