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4107bc7337
PD#OTT-5676 [Problem] digital security team requires OSS to be patched up to the latest or non-vulnerable version [Solution] mm: get rid of vmacache_flush_all() entirely Jann Horn points out that the vmacache_flush_all() function is not only potentially expensive, it's buggy too. It also happens to be entirely unnecessary, because the sequence number overflow case can be avoided by simply making the sequence number be 64-bit. That doesn't even grow the data structures in question, because the other adjacent fields are already 64-bit. So simplify the whole thing by just making the sequence number overflow case go away entirely, which gets rid of all the complications and makes the code faster too. Win-win. [Test] Change-Id: I536c7b183ced970e18c9d67211f32da0ee404111 Signed-off-by: Hanjie Lin <hanjie.lin@amlogic.com>
97 lines
2.1 KiB
C
97 lines
2.1 KiB
C
/*
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* Copyright (C) 2014 Davidlohr Bueso.
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*/
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#include <linux/sched.h>
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#include <linux/mm.h>
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#include <linux/vmacache.h>
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/*
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* This task may be accessing a foreign mm via (for example)
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* get_user_pages()->find_vma(). The vmacache is task-local and this
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* task's vmacache pertains to a different mm (ie, its own). There is
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* nothing we can do here.
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*
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* Also handle the case where a kernel thread has adopted this mm via use_mm().
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* That kernel thread's vmacache is not applicable to this mm.
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*/
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static inline bool vmacache_valid_mm(struct mm_struct *mm)
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{
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return current->mm == mm && !(current->flags & PF_KTHREAD);
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}
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void vmacache_update(unsigned long addr, struct vm_area_struct *newvma)
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{
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if (vmacache_valid_mm(newvma->vm_mm))
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current->vmacache[VMACACHE_HASH(addr)] = newvma;
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}
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static bool vmacache_valid(struct mm_struct *mm)
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{
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struct task_struct *curr;
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if (!vmacache_valid_mm(mm))
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return false;
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curr = current;
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if (mm->vmacache_seqnum != curr->vmacache_seqnum) {
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/*
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* First attempt will always be invalid, initialize
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* the new cache for this task here.
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*/
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curr->vmacache_seqnum = mm->vmacache_seqnum;
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vmacache_flush(curr);
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return false;
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}
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return true;
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}
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struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
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{
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int i;
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count_vm_vmacache_event(VMACACHE_FIND_CALLS);
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if (!vmacache_valid(mm))
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return NULL;
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for (i = 0; i < VMACACHE_SIZE; i++) {
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struct vm_area_struct *vma = current->vmacache[i];
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if (!vma)
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continue;
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if (WARN_ON_ONCE(vma->vm_mm != mm))
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break;
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if (vma->vm_start <= addr && vma->vm_end > addr) {
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count_vm_vmacache_event(VMACACHE_FIND_HITS);
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return vma;
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}
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}
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return NULL;
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}
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#ifndef CONFIG_MMU
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struct vm_area_struct *vmacache_find_exact(struct mm_struct *mm,
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unsigned long start,
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unsigned long end)
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{
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int i;
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count_vm_vmacache_event(VMACACHE_FIND_CALLS);
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if (!vmacache_valid(mm))
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return NULL;
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for (i = 0; i < VMACACHE_SIZE; i++) {
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struct vm_area_struct *vma = current->vmacache[i];
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if (vma && vma->vm_start == start && vma->vm_end == end) {
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count_vm_vmacache_event(VMACACHE_FIND_HITS);
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return vma;
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}
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}
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return NULL;
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}
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#endif
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