linux-kernel - [PATCH] tty: serial: add error handling for try_module

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Date:   Tue, 12 Jun 2018 12:50:46 +0800
From:   Zhouyang Jia <jiazhouyang09@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Zhouyang Jia <jiazhouyang09@...il.com>,
        Jason Wessel <jason.wessel@...driver.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        kgdb-bugreport@...ts.sourceforge.net, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] tty: serial: add error handling for try_module_get

When try_module_get fails, the lack of error-handling code may
cause unexpected results.

This patch adds error-handling code after calling try_module_get.

Signed-off-by: Zhouyang Jia <jiazhouyang09@...il.com>
---
 drivers/tty/serial/kgdboc.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
index b4ba2b1..641e22a 100644
--- a/drivers/tty/serial/kgdboc.c
+++ b/drivers/tty/serial/kgdboc.c
@@ -286,8 +286,10 @@ static void kgdboc_pre_exp_handler(void)
 		con_debug_enter(vc_cons[fg_console].d);
 	}
 	/* Increment the module count when the debugger is active */
-	if (!kgdb_connected)
-		try_module_get(THIS_MODULE);
+	if (!kgdb_connected) {
+		if (!try_module_get(THIS_MODULE))
+			printk(KERN_ERR "kgdboc: cannot get module.\n");
+	}
 }
 
 static void kgdboc_post_exp_handler(void)
-- 
2.7.4