x86/kprobes: Fix __recover_optprobed_insn check optimizing logic

Since the following commit:

  commit f66c044 ("kprobes: Set unoptimized flag after unoptimizing code")

modified the update timing of the KPROBE_FLAG_OPTIMIZED, a optimized_kprobe
may be in the optimizing or unoptimizing state when op.kp->flags
has KPROBE_FLAG_OPTIMIZED and op->list is not empty.

The __recover_optprobed_insn check logic is incorrect, a kprobe in the
unoptimizing state may be incorrectly determined as unoptimizing.
As a result, incorrect instructions are copied.

The optprobe_queued_unopt function needs to be exported for invoking in
arch directory.

Link: https://lore.kernel.org/all/[email protected]/

Fixes: f66c044 ("kprobes: Set unoptimized flag after unoptimizing code")
Cc: [email protected]
Signed-off-by: Yang Jihong <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

Author: Yang Jihong

arch/x86/kernel/kprobes/opt.c

@@ -46,8 +46,8 @@ unsigned long __recover_optprobed_insn(kprobe_opcode_t *buf, unsigned long addr)
 		/* This function only handles jump-optimized kprobe */
 		if (kp && kprobe_optimized(kp)) {
 			op = container_of(kp, struct optimized_kprobe, kp);
-			/* If op->list is not empty, op is under optimizing */
-			if (list_empty(&op->list))
+			/* If op is optimized or under unoptimizing */
+			if (list_empty(&op->list) || optprobe_queued_unopt(op))
 				goto found;
 		}
 	}

include/linux/kprobes.h

@@ -378,6 +378,7 @@ extern void opt_pre_handler(struct kprobe *p, struct pt_regs *regs);
 DEFINE_INSN_CACHE_OPS(optinsn);
 
 extern void wait_for_kprobe_optimizer(void);
+bool optprobe_queued_unopt(struct optimized_kprobe *op);
 #else /* !CONFIG_OPTPROBES */
 static inline void wait_for_kprobe_optimizer(void) { }
 #endif /* CONFIG_OPTPROBES */

kernel/kprobes.c

@@ -660,7 +660,7 @@ void wait_for_kprobe_optimizer(void)
 	mutex_unlock(&kprobe_mutex);
 }
 
-static bool optprobe_queued_unopt(struct optimized_kprobe *op)
+bool optprobe_queued_unopt(struct optimized_kprobe *op)
 {
 	struct optimized_kprobe *_op;