Commit 430af825 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Peter Zijlstra
Browse files

uprobes: kill the unnecessary put_uprobe/xol_free_insn_slot in uprobe_free_utask() 



If pre_ssout() succeeds and sets utask->active_uprobe and utask->xol_vaddr
the task must not exit until it calls handle_singlestep() which does the
necessary put_uprobe() and xol_free_insn_slot().

Remove put_uprobe() and xol_free_insn_slot() from uprobe_free_utask(). With
this change xol_free_insn_slot() can't hit xol_area/utask/xol_vaddr == NULL,
we can kill the unnecessary checks checks and simplify this function more.

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/20240929144239.GA9475@redhat.com
parent c7b4133c

kernel/events/uprobes.c

+5 −19
Original line number Diff line number Diff line
@@ -1673,28 +1673,16 @@ static unsigned long xol_get_insn_slot(struct uprobe *uprobe) 
}



/*

 * xol_free_insn_slot - If slot was earlier allocated by

 * @xol_get_insn_slot(), make the slot available for

 * subsequent requests.

 * xol_free_insn_slot - free the slot allocated by xol_get_insn_slot()

 */

static void xol_free_insn_slot(struct task_struct *tsk)

{

	struct xol_area *area;

	unsigned long slot_addr;

	unsigned long offset;



	if (!tsk->mm || !tsk->mm->uprobes_state.xol_area || !tsk->utask)

		return;



	slot_addr = tsk->utask->xol_vaddr;

	if (unlikely(!slot_addr))

		return;

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

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



	tsk->utask->xol_vaddr = 0;

	area = tsk->mm->uprobes_state.xol_area;

	offset = slot_addr - area->vaddr;

	/*

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

	 * 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) {
@@ -1764,14 +1752,12 @@ void uprobe_free_utask(struct task_struct *t) 
	if (!utask)

		return;



	if (utask->active_uprobe)

		put_uprobe(utask->active_uprobe);

	WARN_ON_ONCE(utask->active_uprobe || utask->xol_vaddr);



	ri = utask->return_instances;

	while (ri)

		ri = free_ret_instance(ri);



	xol_free_insn_slot(t);

	kfree(utask);

	t->utask = NULL;

}