[Acked] [Lucid PATCH 00/10] Backport killable request_module()

[Tetsuo Handa]

Andy Whitcroft wrote:
> It should be easy to test, systems should stop booting right if this is wrong.

Since we can force recompilation of kernel modules upon ABI bump, we could
apply a validator patch (like below untested one) upon next ABI bump (in order
to catch forgotten users) and revert it upon some-time-later ABI rebump.

diff --git a/include/linux/kmod.h b/include/linux/kmod.h
index 9efeae6..1350670 100644
--- a/include/linux/kmod.h
+++ b/include/linux/kmod.h
@@ -48,10 +48,10 @@ static inline int request_module_nowait(const char *name, ...) { return -ENOSYS;
 struct cred;
 struct file;
 
-#define UMH_NO_WAIT	0	/* don't wait at all */
-#define UMH_WAIT_EXEC	1	/* wait for the exec, but not the process */
-#define UMH_WAIT_PROC	2	/* wait for the process to complete */
-#define UMH_KILLABLE	4	/* wait for EXEC/PROC killable */
+#define UMH_NO_WAIT	0x10	/* don't wait at all */
+#define UMH_WAIT_EXEC	0x11	/* wait for the exec, but not the process */
+#define UMH_WAIT_PROC	0x12	/* wait for the process to complete */
+#define UMH_KILLABLE	0x04	/* wait for EXEC/PROC killable */
 
 struct subprocess_info {
 	struct work_struct work;
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 957a7aa..ecfd3d5 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -483,6 +483,18 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
 	DECLARE_COMPLETION_ONSTACK(done);
 	int retval = 0;
 
+	if (unlikely(wait == -1 || wait == 0 || wait == 1)) {
+		WARN(1, "Requesting for usermode helper with hardcoded wait "
+		     "flag. Change to use UMH_* symbols and recompile, or "
+		     "this request will fail on Linux 3.4.\n");
+		if (wait == -1)
+			wait = UMH_NO_WAIT;
+		else if (wait == 0)
+			wait = UMH_WAIT_EXEC;
+		else
+			wait = UMH_WAIT_PROC;
+	}
+
 	helper_lock();
 	if (sub_info->path[0] == '\0')
 		goto out;