powerpc/pseries: Add backward compatibilty to read old kernel oops-log

Older kernels has just length information in their header. Handle it
while reading old kernel oops log from pstore.

Applies on top of powerpc/pseries: Fix buffer overflow when reading from pstore

Signed-off-by: Aruna Balakrishnaiah <aruna@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 14 insertions, 4 deletions

diff --git a/arch/powerpc/platforms/pseries/nvram.c b/arch/powerpc/platforms/pseries/nvram.c
index 893f36053c97..6a5f2b1f32ca 100644
--- a/arch/powerpc/platforms/pseries/nvram.c
+++ b/arch/powerpc/platforms/pseries/nvram.c
@@ -720,15 +720,25 @@ static ssize_t nvram_pstore_read(u64 *id, enum pstore_type_id *type,
 
         if (nvram_type_ids[read_type] == PSTORE_TYPE_DMESG) {
                 int length, unzipped_len;
+                size_t hdr_size;
 
                 oops_hdr = (struct oops_log_info *)buff;
-                length = oops_hdr->report_length;
+                if (oops_hdr->version < OOPS_HDR_VERSION) {
+                        /* Old format oops header had 2-byte record size */
+                        hdr_size = sizeof(u16);
+                        length = oops_hdr->version;
+                        time->tv_sec = 0;
+                        time->tv_nsec = 0;
+                } else {
+                        hdr_size = sizeof(*oops_hdr);
+                        length = oops_hdr->report_length;
+                        time->tv_sec = oops_hdr->timestamp;
+                        time->tv_nsec = 0;
+                }
                 *buf = kmalloc(length, GFP_KERNEL);
                 if (*buf == NULL)
                         return -ENOMEM;
-                memcpy(*buf, buff + sizeof(*oops_hdr), length);
-                time->tv_sec = oops_hdr->timestamp;
-                time->tv_nsec = 0;
+                memcpy(*buf, buff + hdr_size, length);
                 kfree(buff);
 
                 if (err_type == ERR_TYPE_KERNEL_PANIC_GZ) {