dmi: prevent linked list corruption

Adding the same item to a given linked list more than once is guaranteed
to break and corrupt the list.  This is however what we do in dmi_scan
since commit 79da4721117fcf188b4b007b775738a530f574da ("x86: fix DMI out
of memory problems").

Given that there is absolutely no interest in saving empty OEM strings
anyway, I propose the simple and efficient fix below: we discard the empty
OEM strings altogether.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Parag Warudkar <parag.warudkar@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Matt Domsch <Matt_Domsch@dell.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/firmware/dmi_scan.c

@@ -217,10 +217,6 @@ static void __init dmi_save_devices(const struct dmi_header *dm)
 	}
 }
 
-static struct dmi_device empty_oem_string_dev = {
-	.name = dmi_empty_string,
-};
-
 static void __init dmi_save_oem_strings_devices(const struct dmi_header *dm)
 {
 	int i, count = *(u8 *)(dm + 1);
@@ -229,10 +225,8 @@ static void __init dmi_save_oem_strings_devices(const struct dmi_header *dm)
 	for (i = 1; i <= count; i++) {
 		char *devname = dmi_string(dm, i);
 
-		if (!strcmp(devname, dmi_empty_string)) {
-			list_add(&empty_oem_string_dev.list, &dmi_devices);
+		if (devname == dmi_empty_string)
 			continue;
-		}
 
 		dev = dmi_alloc(sizeof(*dev));
 		if (!dev) {