linux-kernel - [PATCH] MIPS: Fix highmem crash in __update

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Date:	Wed, 15 Apr 2015 15:10:54 +0200
From:	Lars Persson <lars.persson@...s.com>
To:	ralf@...ux-mips.org, linux-mips@...ux-mips.org,
	linux-kernel@...r.kernel.org
Cc:	Lars Persson <larper@...s.com>
Subject: [PATCH] MIPS: Fix highmem crash in __update_cache.

Due to a change in flush_dcache_page, highmem pages may have the
dcache dirty flag set. Until there is proper support for highmen in
cache.c we must filter out highmem pages to avoid NULL pointer
dereferences.

Signed-off-by: Lars Persson <larper@...s.com>
---
 arch/mips/mm/cache.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
index 77d96db..46136f6 100644
--- a/arch/mips/mm/cache.c
+++ b/arch/mips/mm/cache.c
@@ -142,6 +142,10 @@ void __update_cache(struct vm_area_struct *vma, unsigned long address,
 	if (unlikely(!pfn_valid(pfn)))
 		return;
 	page = pfn_to_page(pfn);
+
+	if (PageHighMem(page))
+		return;
+
 	if (page_mapping(page) && Page_dcache_dirty(page)) {
 		addr = (unsigned long) page_address(page);
 		if (exec || pages_do_alias(addr, address & PAGE_MASK))
-- 
1.7.10.4

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