intel_th: msu: Fix missing allocation failure check on a kstrndup

Commit 615c164 ("intel_th: msu: Introduce buffer interface") forgot
to add a NULL pointer check for the value returned from kstrdup(), which
will be troublesome if the allocation fails.

Fix that by adding the check.

Addresses-Coverity: ("Dereference null return")
Fixes: 615c164 ("intel_th: msu: Introduce buffer interface")
Signed-off-by: Colin Ian King <[email protected]>
[alexander.shishkin: amended the commit message]
Signed-off-by: Alexander Shishkin <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Link: https://lore.kernel.org/lkml/[email protected]/
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Colin Ian King

drivers/hwtracing/intel_th/msu.c

@@ -1848,6 +1848,9 @@ mode_store(struct device *dev, struct device_attribute *attr, const char *buf,
 		len = cp - buf;
 
 	mode = kstrndup(buf, len, GFP_KERNEL);
+	if (!mode)
+		return -ENOMEM;
+
 	i = match_string(msc_mode, ARRAY_SIZE(msc_mode), mode);
 	if (i >= 0)
 		goto found;