[MIPS] Fix aliasing bug in copy_user_highpage. (b868868a) · Commits · 戴 / test

Copy_user_highpage was written assuming it was only being called for breaking COW pages in which case the source page isn't cached as in marked cachable under it kernel virtual address. If it is called anyway the aliasing avoidance strategy implemented by kmap_coherent will fail. Avoid the use of kmap_coherent for pages marked dirty and to avoid another instance of this sort of bug, place a BUG_ON in kmap_coherent. Signed-off-by:

Ralf Baechle <ralf@linux-mips.org>

arch/mips/mm/init.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -8,6 +8,7 @@
		* Kevin D. Kissell, kevink@mips.com and Carsten Langgaard, carstenl@mips.com
		* Copyright (C) 2000 MIPS Technologies, Inc. All rights reserved.
		*/
		#include <linux/bug.h>
		#include <linux/init.h>
		#include <linux/module.h>
		#include <linux/signal.h>
		@@ -132,6 +133,8 @@ void kmap_coherent(struct page page, unsigned long addr)
		pte_t pte;
		int tlbidx;

		BUG_ON(Page_dcache_dirty(page));

		inc_preempt_count();
		idx = (addr >> PAGE_SHIFT) & (FIX_N_COLOURS - 1);
		#ifdef CONFIG_MIPS_MT_SMTC
		@@ -208,7 +211,7 @@ void copy_user_highpage(struct page to, struct page from,
		void vfrom, vto;

		vto = kmap_atomic(to, KM_USER1);
		if (cpu_has_dc_aliases) {
		if (cpu_has_dc_aliases && !Page_dcache_dirty(from)) {
		vfrom = kmap_coherent(from, vaddr);
		copy_page(vto, vfrom);
		kunmap_coherent();

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