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uprobes: deny mremap(xol_vma)
kernel/events/uprobes.c assumes that xol_area->vaddr is always correct but a malicious application can remap its "[uprobes]" vma to another adress to confuse the kernel. Introduce xol_mremap() to make this impossible. With this change utask->xol_vaddr in xol_free_insn_slot() can't be invalid, we can turn the offset check into WARN_ON_ONCE(offset >= PAGE_SIZE). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20240929144258.GA9492@redhat.com
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@ -1472,9 +1472,15 @@ static vm_fault_t xol_fault(const struct vm_special_mapping *sm,
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return 0;
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}
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static int xol_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma)
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{
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return -EPERM;
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}
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static const struct vm_special_mapping xol_mapping = {
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.name = "[uprobes]",
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.fault = xol_fault,
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.mremap = xol_mremap,
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};
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/* Slot allocation for XOL */
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@ -1667,21 +1673,19 @@ static void xol_free_insn_slot(struct uprobe_task *utask)
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{
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struct xol_area *area = current->mm->uprobes_state.xol_area;
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unsigned long offset = utask->xol_vaddr - area->vaddr;
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unsigned int slot_nr;
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utask->xol_vaddr = 0;
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/*
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* xol_vaddr must fit into [area->vaddr, area->vaddr + PAGE_SIZE).
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* This check can only fail if the "[uprobes]" vma was mremap'ed.
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*/
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if (offset < PAGE_SIZE) {
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int slot_nr = offset / UPROBE_XOL_SLOT_BYTES;
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/* xol_vaddr must fit into [area->vaddr, area->vaddr + PAGE_SIZE) */
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if (WARN_ON_ONCE(offset >= PAGE_SIZE))
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return;
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clear_bit(slot_nr, area->bitmap);
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atomic_dec(&area->slot_count);
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smp_mb__after_atomic(); /* pairs with prepare_to_wait() */
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if (waitqueue_active(&area->wq))
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wake_up(&area->wq);
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}
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slot_nr = offset / UPROBE_XOL_SLOT_BYTES;
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clear_bit(slot_nr, area->bitmap);
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atomic_dec(&area->slot_count);
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smp_mb__after_atomic(); /* pairs with prepare_to_wait() */
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if (waitqueue_active(&area->wq))
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wake_up(&area->wq);
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}
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void __weak arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
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