Skip to content

Commit

Permalink
uprobes: deny mremap(xol_vma)
Browse files Browse the repository at this point in the history
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
  • Loading branch information
Oleg Nesterov authored and Peter Zijlstra committed Oct 7, 2024
1 parent c5356ab commit c16e2fd
Showing 1 changed file with 17 additions and 13 deletions.
30 changes: 17 additions & 13 deletions kernel/events/uprobes.c
Original file line number Diff line number Diff line change
Expand Up @@ -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 */
Expand Down Expand Up @@ -1667,21 +1673,19 @@ 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;

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);
}
/* 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,
Expand Down

0 comments on commit c16e2fd

Please sign in to comment.