From: Tiezhu Yang <yangtiezhu@loongson.cn>
To: Luis Chamberlain <mcgrof@kernel.org>,
Shuah Khan <shuah@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Jessica Yu <jeyu@kernel.org>
Cc: linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org,
Markus Elfring <Markus.Elfring@web.de>,
Xuefeng Li <lixuefeng@loongson.cn>
Subject: [PATCH v3 3/4] kmod: Return directly if module name is empty in request_module()
Date: Mon, 20 Apr 2020 20:33:54 +0800 [thread overview]
Message-ID: <1587386035-5188-4-git-send-email-yangtiezhu@loongson.cn> (raw)
In-Reply-To: <1587386035-5188-1-git-send-email-yangtiezhu@loongson.cn>
If module name is empty, it is better to return directly at the beginning
of request_module() without doing the needless call_modprobe() operation.
Call trace:
request_module()
|
|
__request_module()
|
|
call_modprobe()
|
|
call_usermodehelper_exec() -- retval = sub_info->retval;
|
|
call_usermodehelper_exec_work()
|
|
call_usermodehelper_exec_sync() -- sub_info->retval = ret;
|
| --> call_usermodehelper_exec_async() --> do_execve()
|
kernel_wait4(pid, (int __user *)&ret, 0, NULL);
sub_info->retval is 256 after call kernel_wait4(), the function
call_usermodehelper_exec() returns sub_info->retval which is 256,
then call_modprobe() and __request_module() returns 256.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
v3:
- no changes
v2:
- update the commit message to explain the detailed reason
kernel/kmod.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 3cd075c..5851444 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -28,6 +28,8 @@
#include <trace/events/module.h>
+#define MODULE_NOT_FOUND 256
+
/*
* Assuming:
*
@@ -144,6 +146,9 @@ int __request_module(bool wait, const char *fmt, ...)
if (ret >= MODULE_NAME_LEN)
return -ENAMETOOLONG;
+ if (strlen(module_name) == 0)
+ return MODULE_NOT_FOUND;
+
ret = security_kernel_module_request(module_name);
if (ret)
return ret;
--
2.1.0
next prev parent reply other threads:[~2020-04-20 12:34 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-20 12:33 [PATCH v3 0/4] Fix some issues about kmod Tiezhu Yang
2020-04-20 12:33 ` [PATCH v3 1/4] selftests: kmod: Use variable NAME in kmod_test_0001() Tiezhu Yang
2020-04-20 12:33 ` [PATCH v3 2/4] kmod: Remove redundant "be an" in the comment Tiezhu Yang
2020-04-20 12:33 ` Tiezhu Yang [this message]
2020-04-20 18:19 ` [PATCH v3 3/4] kmod: Return directly if module name is empty in request_module() Luis Chamberlain
2020-04-21 3:07 ` Tiezhu Yang
2020-04-21 14:49 ` Jessica Yu
2020-04-22 8:31 ` Luis Chamberlain
2020-04-22 8:55 ` Tiezhu Yang
2020-04-22 9:01 ` Luis Chamberlain
2020-04-20 12:33 ` [PATCH v3 4/4] test_kmod: Avoid potential double free in trigger_config_run_type() Tiezhu Yang
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