Commit c16e2fdd authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Peter Zijlstra
Browse files

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: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240929144258.GA9492@redhat.com
parent c5356ab1

kernel/events/uprobes.c

+17 −13
Original line number Diff line number Diff line
@@ -1472,9 +1472,15 @@ static vm_fault_t xol_fault(const struct vm_special_mapping *sm, 
	return 0;

}



static int xol_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma)

{

	return -EPERM;

}



static const struct vm_special_mapping xol_mapping = {

	.name = "[uprobes]",

	.fault = xol_fault,

	.mremap = xol_mremap,

};



/* Slot allocation for XOL */
@@ -1667,22 +1673,20 @@ static void xol_free_insn_slot(struct uprobe_task *utask) 
{

	struct xol_area *area = current->mm->uprobes_state.xol_area;

	unsigned long offset = utask->xol_vaddr - area->vaddr;

	unsigned int slot_nr;



	utask->xol_vaddr = 0;

	/*

	 * xol_vaddr must fit into [area->vaddr, area->vaddr + PAGE_SIZE).

	 * This check can only fail if the "[uprobes]" vma was mremap'ed.

	 */

	if (offset < PAGE_SIZE) {

		int slot_nr = offset / UPROBE_XOL_SLOT_BYTES;

	/* xol_vaddr must fit into [area->vaddr, area->vaddr + PAGE_SIZE) */

	if (WARN_ON_ONCE(offset >= PAGE_SIZE))

		return;



	slot_nr = offset / UPROBE_XOL_SLOT_BYTES;

	clear_bit(slot_nr, area->bitmap);

	atomic_dec(&area->slot_count);

	smp_mb__after_atomic(); /* pairs with prepare_to_wait() */

	if (waitqueue_active(&area->wq))

		wake_up(&area->wq);

}

}



void __weak arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,

				  void *src, unsigned long len)