nvram: force re-verification after writing

The running OS is free to re-write the contents of NVRAM. The skiboot
NVRAM parser relies on the NVRAM contents being valid so we need to
force the NVRAM contents to be revalidated after the host OS has written
to it.

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

1 files changed, 19 insertions, 4 deletions

diff --git a/core/nvram-format.c b/core/nvram-format.c
index 227147e..b98aee1 100644
--- a/core/nvram-format.c
+++ b/core/nvram-format.c
@@ -208,12 +208,27 @@ static const char *find_next_key(const char *start, const char *end)
  */
 const char *nvram_query(const char *key)
 {
-	const char *part_end = (const char *) skiboot_part_hdr +
-		skiboot_part_hdr->len * 16 - 1;
-	const char *start = (const char *) skiboot_part_hdr +
-		sizeof(*skiboot_part_hdr);
+	const char *part_end, *start;
 	int key_len = strlen(key);
 
+	/*
+	 * The running OS can modify the NVRAM as it pleases so we need to be
+	 * a little paranoid and check that it's ok before we try parse it.
+	 *
+	 * NB: nvram_validate() can update skiboot_part_hdr
+	 */
+	if (!nvram_validate()) {
+		prerror("NVRAM: Look up for '%s' failed due to bad format!\n",
+			key);
+		return NULL;
+	}
+
+	part_end = (const char *) skiboot_part_hdr
+		+ skiboot_part_hdr->len * 16 - 1;
+
+	start = (const char *) skiboot_part_hdr
+		+ sizeof(*skiboot_part_hdr);
+
 	if (!key_len) {
 		prlog(PR_WARNING, "NVRAM: search key is empty!\n");
 		return NULL;