[PATCH] ppc64: fix nvram partition scan

[Utz Bacher]

Hi Paul and all,

the following patch against 2.6.11-rc4 corrects some problems with bad NVRAM
contents:
- when the checksum is incorrect, better do not trust anything (instead
   of assuming the length is correct)
- when the partition length is zero, stop looking for more partitions
   instead of looping

Please consider for inclusion.

Regards,
Utz

Signed-off-by: Utz Bacher <utz.bacher at de.ibm.com>

Index: linux-2.6.11-rc4/arch/ppc64/kernel/nvram.c
===================================================================
--- linux-2.6.11-rc4.orig/arch/ppc64/kernel/nvram.c
+++ linux-2.6.11-rc4/arch/ppc64/kernel/nvram.c
@@ -535,9 +535,21 @@
 		memcpy(&phead, header, NVRAM_HEADER_LEN);

 		c_sum = nvram_checksum(&phead);
-		if (c_sum != phead.checksum)
-			printk(KERN_WARNING "WARNING: nvram partition checksum "
-			       "was %02x, should be %02x!\n", phead.checksum, c_sum);
+		if (c_sum != phead.checksum) {
+			printk(KERN_WARNING "WARNING: nvram partition "
+			       "checksum was %02x, should be %02x! Skipping "
+			       "subsequent partitions to prevent data loss\n",
+			       phead.checksum, c_sum);
+			kfree(header);
+			return size;
+		}
+
+		if (!phead.length) {
+			printk(KERN_WARNING "nvram partition chain ends "
+			       "(zero partition length). Assuming end "
+			       "of chain.\n");
+			break;
+		}

 		tmp_part = (struct nvram_partition *)
 			kmalloc(sizeof(struct nvram_partition), GFP_KERNEL);