Merge tag 'probes-fixes-v6.7-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull probes fixes from Masami Hiramatsu:

 - objpool: Fix objpool overrun case on memory/cache access delay
   especially on the big.LITTLE SoC. The objpool uses a copy of object
   slot index internal loop, but the slot index can be changed on
   another processor in parallel. In that case, the difference of 'head'
   local copy and the 'slot->last' index will be bigger than local slot
   size. In that case, we need to re-read the slot::head to update it.

 - kretprobe: Fix to use appropriate rcu API for kretprobe holder. Since
   kretprobe_holder::rp is RCU managed, it should use
   rcu_assign_pointer() and rcu_dereference_check() correctly. Also
   adding __rcu tag for finding wrong usage by sparse.

 - rethook: Fix to use appropriate rcu API for rethook::handler. The
   same as kretprobe, rethook::handler is RCU managed and it should use
   rcu_assign_pointer() and rcu_dereference_check(). This also adds
   __rcu tag for finding wrong usage by sparse.

* tag 'probes-fixes-v6.7-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  rethook: Use __rcu pointer for rethook::handler
  kprobes: consistent rcu api usage for kretprobe holder
  lib: objpool: fix head overrun on RK3588 SBC

2 files changed, 10 insertions, 10 deletions

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index ab1da3142b06..0ff44d6633e3 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -139,7 +139,7 @@ static inline bool kprobe_ftrace(struct kprobe *p)
  *
  */
 struct kretprobe_holder {
-	struct kretprobe	*rp;
+	struct kretprobe __rcu *rp;
 	struct objpool_head	pool;
 };
 
@@ -197,10 +197,8 @@ extern int arch_trampoline_kprobe(struct kprobe *p);
 #ifdef CONFIG_KRETPROBE_ON_RETHOOK
 static nokprobe_inline struct kretprobe *get_kretprobe(struct kretprobe_instance *ri)
 {
-	RCU_LOCKDEP_WARN(!rcu_read_lock_any_held(),
-		"Kretprobe is accessed from instance under preemptive context");
-
-	return (struct kretprobe *)READ_ONCE(ri->node.rethook->data);
+	/* rethook::data is non-changed field, so that you can access it freely. */
+	return (struct kretprobe *)ri->node.rethook->data;
 }
 static nokprobe_inline unsigned long get_kretprobe_retaddr(struct kretprobe_instance *ri)
 {
@@ -245,10 +243,7 @@ unsigned long kretprobe_trampoline_handler(struct pt_regs *regs,
 
 static nokprobe_inline struct kretprobe *get_kretprobe(struct kretprobe_instance *ri)
 {
-	RCU_LOCKDEP_WARN(!rcu_read_lock_any_held(),
-		"Kretprobe is accessed from instance under preemptive context");
-
-	return READ_ONCE(ri->rph->rp);
+	return rcu_dereference_check(ri->rph->rp, rcu_read_lock_any_held());
 }
 
 static nokprobe_inline unsigned long get_kretprobe_retaddr(struct kretprobe_instance *ri)
diff --git a/include/linux/rethook.h b/include/linux/rethook.h
index ce69b2b7bc35..ba60962805f6 100644
--- a/include/linux/rethook.h
+++ b/include/linux/rethook.h
@@ -28,7 +28,12 @@ typedef void (*rethook_handler_t) (struct rethook_node *, void *, unsigned long,
  */
 struct rethook {
 	void			*data;
-	rethook_handler_t	handler;
+	/*
+	 * To avoid sparse warnings, this uses a raw function pointer with
+	 * __rcu, instead of rethook_handler_t. But this must be same as
+	 * rethook_handler_t.
+	 */
+	void (__rcu *handler) (struct rethook_node *, void *, unsigned long, struct pt_regs *);
 	struct objpool_head	pool;
 	struct rcu_head		rcu;
 };