pstore: don't OOPS when there are no ftrace zones

We'll OOPS in ramoops_get_next_prz() if the platform didn't ask for any
ftrace zones (i.e., cxt->fprzs will be NULL). Let's just skip this
entire FTRACE section if there's no 'fprzs'.

Regression seen on a coreboot/depthcharge-based Chromebook.

Fixes: 2fbea82bbb89 ("pstore: Merge per-CPU ftrace records into one")
Cc: Joel Fernandes <joelaf@google.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 27c059e1760a8918a0dde19cb884c5ff4563606c..1d887efaaf718c497a233b63286914cd9a498a00 100644 (file)
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -280,7 +280,7 @@ static ssize_t ramoops_pstore_read(u64 *id, enum pstore_type_id *type,
                                           1, id, type, PSTORE_TYPE_PMSG, 0);
 
        /* ftrace is last since it may want to dynamically allocate memory. */
-       if (!prz_ok(prz)) {
+       if (!prz_ok(prz) && cxt->fprzs) {
                if (!(cxt->flags & RAMOOPS_FLAG_FTRACE_PER_CPU)) {
                        prz = ramoops_get_next_prz(cxt->fprzs,
                                        &cxt->ftrace_read_cnt, 1, id, type,