From 5766b842b23c6b40935a5f3bd435b2bcdaff2143 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Tue, 20 Jan 2009 09:13:15 +0100 Subject: [PATCH] x86, cpumask: fix tlb flush race Impact: fix bootup crash The cpumask is now passed in as a reference to mm->cpu_vm_mask, not on the stack - hence it is not constant anymore during the TLB flush. That way it could race and some static sanity checks would trigger: [ 238.154287] ------------[ cut here ]------------ [ 238.156039] kernel BUG at arch/x86/kernel/tlb_32.c:130! [ 238.156039] invalid opcode: 0000 [#1] SMP [ 238.156039] last sysfs file: /sys/class/net/eth2/address [ 238.156039] Modules linked in: [ 238.156039] [ 238.156039] Pid: 6493, comm: ifup-eth Not tainted (2.6.29-rc2-tip #1) P4DC6 [ 238.156039] EIP: 0060:[] EFLAGS: 00010202 CPU: 2 [ 238.156039] EIP is at native_flush_tlb_others+0x35/0x158 [ 238.156039] EAX: c0ef972c EBX: f6143301 ECX: 00000000 EDX: 00000000 [ 238.156039] ESI: f61433a8 EDI: f6143200 EBP: f34f3e00 ESP: f34f3df0 [ 238.156039] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 [ 238.156039] Process ifup-eth (pid: 6493, ti=f34f2000 task=f399ab00 task.ti=f34f2000) [ 238.156039] Stack: [ 238.156039] ffffffff f61433a8 ffffffff f6143200 f34f3e18 c0118e9c 00000000 f6143200 [ 238.156039] f61433a8 f5bec738 f34f3e28 c0119435 c2b5b830 f6143200 f34f3e34 c01c2dc3 [ 238.156039] bffd9000 f34f3e60 c01c3051 00000000 ffffffff f34f3e4c 00000000 00000071 [ 238.156039] Call Trace: [ 238.156039] [] ? flush_tlb_others+0x52/0x5b [ 238.156039] [] ? flush_tlb_mm+0x7f/0x8b [ 238.156039] [] ? tlb_finish_mmu+0x2d/0x55 [ 238.156039] [] ? exit_mmap+0x124/0x170 [ 238.156039] [] ? mmput+0x40/0xf5 [ 238.156039] [] ? flush_old_exec+0x640/0x94b [ 238.156039] [] ? fsnotify_access+0x37/0x39 [ 238.156039] [] ? kernel_read+0x39/0x4b [ 238.156039] [] ? load_elf_binary+0x4a1/0x11bb [ 238.156039] [] ? might_fault+0x51/0x9c [ 238.156039] [] ? paravirt_read_tsc+0x20/0x4f [ 238.156039] [] ? native_sched_clock+0x5d/0x60 [ 238.156039] [] ? search_binary_handler+0xab/0x2c4 [ 238.156039] [] ? load_elf_binary+0x0/0x11bb [ 238.156039] [] ? _raw_read_unlock+0x21/0x46 [ 238.156039] [] ? load_elf_binary+0x0/0x11bb [ 238.156039] [] ? search_binary_handler+0xb2/0x2c4 [ 238.156039] [] ? do_execve+0x21c/0x2ee [ 238.156039] [] ? sys_execve+0x51/0x8c [ 238.156039] [] ? sysenter_do_call+0x12/0x43 Fix it by not assuming that the cpumask is constant. Signed-off-by: Ingo Molnar --- arch/x86/kernel/tlb_32.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/tlb_32.c b/arch/x86/kernel/tlb_32.c index ec53818f4e38..d37bbfcb813d 100644 --- a/arch/x86/kernel/tlb_32.c +++ b/arch/x86/kernel/tlb_32.c @@ -125,9 +125,8 @@ void native_flush_tlb_others(const struct cpumask *cpumask, struct mm_struct *mm, unsigned long va) { /* - * - mask must exist :) + * mm must exist :) */ - BUG_ON(cpumask_empty(cpumask)); BUG_ON(!mm); /* @@ -138,14 +137,18 @@ void native_flush_tlb_others(const struct cpumask *cpumask, spin_lock(&tlbstate_lock); cpumask_andnot(flush_cpumask, cpumask, cpumask_of(smp_processor_id())); -#ifdef CONFIG_HOTPLUG_CPU - /* If a CPU which we ran on has gone down, OK. */ cpumask_and(flush_cpumask, flush_cpumask, cpu_online_mask); + + /* + * If a task whose mm mask we are looking at has descheduled and + * has cleared its presence from the mask, or if a CPU which we ran + * on has gone down then there might be no flush work left: + */ if (unlikely(cpumask_empty(flush_cpumask))) { spin_unlock(&tlbstate_lock); return; } -#endif + flush_mm = mm; flush_va = va; -- 2.34.1