pstore/ram: verify ramoops header before saving record

On some devices the persistent memory contains junk after a cold boot,
and /dev/pstore/dmesg-ramoops-* are created with random data which is
not the result of a kernel crash.

This patch adds a ramoops header check and skips any
persistent_ram_zone that does not have a valid header.

Signed-off-by: Ben Zhang <benzh@chromium.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index f29373d..d84ce22 100644 (file)
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -186,12 +186,34 @@ static ssize_t ramoops_pstore_read(u64 *id, enum pstore_type_id *type,
        ssize_t size;
        ssize_t ecc_notice_size;
        struct ramoops_context *cxt = psi->data;
-       struct persistent_ram_zone *prz;
-       int header_length;
+       struct persistent_ram_zone *prz = NULL;
+       int header_length = 0;
+
+       /* Ramoops headers provide time stamps for PSTORE_TYPE_DMESG, but
+        * PSTORE_TYPE_CONSOLE and PSTORE_TYPE_FTRACE don't currently have
+        * valid time stamps, so it is initialized to zero.
+        */
+       time->tv_sec = 0;
+       time->tv_nsec = 0;
+       *compressed = false;
+
+       /* Find the next valid persistent_ram_zone for DMESG */
+       while (cxt->dump_read_cnt < cxt->max_dump_cnt && !prz) {
+               prz = ramoops_get_next_prz(cxt->przs, &cxt->dump_read_cnt,
+                                          cxt->max_dump_cnt, id, type,
+                                          PSTORE_TYPE_DMESG, 1);
+               if (!prz_ok(prz))
+                       continue;
+               header_length = ramoops_read_kmsg_hdr(persistent_ram_old(prz),
+                                                     time, compressed);
+               /* Clear and skip this DMESG record if it has no valid header */
+               if (!header_length) {
+                       persistent_ram_free_old(prz);
+                       persistent_ram_zap(prz);
+                       prz = NULL;
+               }
+       }
 
-       prz = ramoops_get_next_prz(cxt->przs, &cxt->dump_read_cnt,
-                                  cxt->max_dump_cnt, id, type,
-                                  PSTORE_TYPE_DMESG, 1);
        if (!prz_ok(prz))
                prz = ramoops_get_next_prz(&cxt->cprz, &cxt->console_read_cnt,
                                           1, id, type, PSTORE_TYPE_CONSOLE, 0);
@@ -204,13 +226,7 @@ static ssize_t ramoops_pstore_read(u64 *id, enum pstore_type_id *type,
        if (!prz_ok(prz))
                return 0;
 
-       if (!persistent_ram_old(prz))
-               return 0;
-
-       size = persistent_ram_old_size(prz);
-       header_length = ramoops_read_kmsg_hdr(persistent_ram_old(prz), time,
-                       compressed);
-       size -= header_length;
+       size = persistent_ram_old_size(prz) - header_length;
 
        /* ECC correction notice */
        ecc_notice_size = persistent_ram_ecc_string(prz, NULL, 0);