[PATCH] fprobe: Fix to ensure the number of active retprobes is not zero

["Masami Hiramatsu (Google)" <mhiramat@kernel.org>]

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

The number of active retprobes can be zero but it is not acceptable,
so return EINVAL error if detected.

Reported-by: wuqiang.matt <wuqiang.matt@bytedance.com>
Closes: https://lore.kernel.org/all/20231016222103.cb9f426edc60220eabd8aa6a@kernel.org/
Fixes: 5b0ab78998e3 ("fprobe: Add exit_handler support")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 kernel/trace/fprobe.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index 3b21f4063258..881f90f0cbcf 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -189,7 +189,7 @@ static int fprobe_init_rethook(struct fprobe *fp, int num)
 {
 	int i, size;
 
-	if (num < 0)
+	if (num <= 0)
 		return -EINVAL;
 
 	if (!fp->exit_handler) {
@@ -202,8 +202,8 @@ static int fprobe_init_rethook(struct fprobe *fp, int num)
 		size = fp->nr_maxactive;
 	else
 		size = num * num_possible_cpus() * 2;
-	if (size < 0)
-		return -E2BIG;
+	if (size <= 0)
+		return -EINVAL;
 
 	fp->rethook = rethook_alloc((void *)fp, fprobe_exit_handler);
 	if (!fp->rethook)