linux-kernel - [PATCH] UBI: cleanup usage of try_module

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Date:	Wed, 11 Jul 2007 17:11:45 +0900
From:	Fernando Luis Vázquez Cao 
	<fernando@....ntt.co.jp>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	dedekind@...radead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] UBI: cleanup usage of try_module_get

The use of try_module_get(THIS_MODULE) in ubi_get_device_info does not
offer real protection against unexpected driver unloads, since we could
be preempted before try_modules_get gets executed. It is the caller who
should manipulate the refcounts. Besides, ubi_get_device_info is an
exported symbol which guarantees protection when accessed through
symbol_get.

Signed-off-by: Fernando Luis Vazquez Cao <fernando@....ntt.co.jp>
---

diff -urNp linux-2.6.22-orig/drivers/mtd/ubi/kapi.c linux-2.6.22/drivers/mtd/ubi/kapi.c
--- linux-2.6.22-orig/drivers/mtd/ubi/kapi.c	2007-07-09 08:32:17.000000000 +0900
+++ linux-2.6.22/drivers/mtd/ubi/kapi.c	2007-07-11 16:34:10.000000000 +0900
@@ -37,12 +37,8 @@ int ubi_get_device_info(int ubi_num, str
 {
 	const struct ubi_device *ubi;
 
-	if (!try_module_get(THIS_MODULE))
-		return -ENODEV;
-
 	if (ubi_num < 0 || ubi_num >= UBI_MAX_DEVICES ||
 	    !ubi_devices[ubi_num]) {
-		module_put(THIS_MODULE);
 		return -ENODEV;
 	}
 
@@ -52,7 +48,6 @@ int ubi_get_device_info(int ubi_num, str
 	di->min_io_size = ubi->min_io_size;
 	di->ro_mode = ubi->ro_mode;
 	di->cdev = MKDEV(ubi->major, 0);
-	module_put(THIS_MODULE);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(ubi_get_device_info);


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