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 ---
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;