uprobes: don't abuse get_utask() in pre_ssout() and prepare_uretprobe()

handle_swbp() calls get_utask() before prepare_uretprobe() or pre_ssout()
can be called, they can simply use current->utask which can't be NULL.

Signed-off-by: Oleg Nesterov <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: oleg-nesterov

kernel/events/uprobes.c

@@ -1905,18 +1905,14 @@ static void cleanup_return_instances(struct uprobe_task *utask, bool chained,
 
 static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
 {
-	struct return_instance *ri;
-	struct uprobe_task *utask;
+	struct uprobe_task *utask = current->utask;
 	unsigned long orig_ret_vaddr, trampoline_vaddr;
+	struct return_instance *ri;
 	bool chained;
 
 	if (!get_xol_area())
 		return;
 
-	utask = get_utask();
-	if (!utask)
-		return;
-
 	if (utask->depth >= MAX_URETPROBE_DEPTH) {
 		printk_ratelimited(KERN_INFO "uprobe: omit uretprobe due to"
 				" nestedness limit pid/tgid=%d/%d\n",
@@ -1977,14 +1973,10 @@ static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
 static int
 pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long bp_vaddr)
 {
-	struct uprobe_task *utask;
+	struct uprobe_task *utask = current->utask;
 	unsigned long xol_vaddr;
 	int err;
 
-	utask = get_utask();
-	if (!utask)
-		return -ENOMEM;
-
 	if (!try_get_uprobe(uprobe))
 		return -EINVAL;