param: fix charp parameters set via sysfs: FIX

We can't kmalloc at early cmdline parsing.

Reported-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Tested-by: Christof Schmitt <christof.schmitt@de.ibm.com>
---
 kernel/params.c |   14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/kernel/params.c b/kernel/params.c
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -223,10 +223,16 @@ int param_set_charp(const char *val, str
 	if (kp->perm & KPARAM_KMALLOCED)
 		kfree(*(char **)kp->arg);
 
-	kp->perm |= KPARAM_KMALLOCED;
-	*(char **)kp->arg = kstrdup(val, GFP_KERNEL);
-	if (!kp->arg)
-		return -ENOMEM;
+	/* This is a hack.  We can't need to strdup in early boot, and we
+	 * don't need to; this mangled commandline is preserved. */
+	if (slab_is_available()) {
+		kp->perm |= KPARAM_KMALLOCED;
+		*(char **)kp->arg = kstrdup(val, GFP_KERNEL);
+		if (!kp->arg)
+			return -ENOMEM;
+	} else
+		*(const char **)kp->arg = val;
+
 	return 0;
 }