Commit 22478677 authored Mar 17, 2013 by Huacai Chen Committed by Ralf Baechle May 08, 2013

MIPS: Init new mmu_context for each possible CPU to avoid memory corruption



Currently, init_new_context() only for each online CPU, this may cause
memory corruption when CPU hotplug and fork() happens at the same time.
To avoid this, we make init_new_context() cover each possible CPU.

Scenario:
1, CPU#1 is being offline;
2, On CPU#0, do_fork() call dup_mm() and copy a mm_struct to the child;
3, On CPU#0, dup_mm() call init_new_context(), since CPU#1 is offline
   and init_new_context() only covers the online CPUs, child has the
   same asid as its parent on CPU#1 (however, child's asid should be 0);
4, CPU#1 is being online;
5, Now, if both parent and child run on CPU#1, memory corruption (e.g.
   segfault, bus error, etc.) will occur.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Acked-by: David Daney <david.daney@cavium.com>
Patchwork: http://patchwork.linux-mips.org/patch/4995/


Acked-by: John Crispin <blogic@openwrt.org>

parent 8759934e

arch/mips/include/asm/mmu_context.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -133,7 +133,7 @@ init_new_context(struct task_struct tsk, struct mm_struct mm)
		{
		int i;

		for_each_online_cpu(i)
		for_each_possible_cpu(i)
		cpu_context(i, mm) = 0;

		return 0;