time: create __getnstimeofday for WARNless calls

The pstore RAM backend can get called during resume, and must be defensive
against a suspended time source. Expose getnstimeofday logic that returns
an error instead of a WARN. This can be detected and the timestamp can
be zeroed out.

Reported-by: Doug Anderson <dianders@chromium.org>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>

1 files changed, 7 insertions, 3 deletions

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 1a4f6da58eab..dacfe78aee7e 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -168,12 +168,16 @@ static ssize_t ramoops_pstore_read(u64 *id, enum pstore_type_id *type,
 static size_t ramoops_write_kmsg_hdr(struct persistent_ram_zone *prz)
 {
         char *hdr;
-        struct timeval timestamp;
+        struct timespec timestamp;
         size_t len;
 
-        do_gettimeofday(&timestamp);
+        /* Report zeroed timestamp if called before timekeeping has resumed. */
+        if (__getnstimeofday(&timestamp)) {
+                timestamp.tv_sec = 0;
+                timestamp.tv_nsec = 0;
+        }
         hdr = kasprintf(GFP_ATOMIC, RAMOOPS_KERNMSG_HDR "%lu.%lu\n",
-                (long)timestamp.tv_sec, (long)timestamp.tv_usec);
+                (long)timestamp.tv_sec, (long)(timestamp.tv_nsec / 1000));
         WARN_ON_ONCE(!hdr);
         len = hdr ? strlen(hdr) : 0;
         persistent_ram_write(prz, hdr, len);