Commit 30696378 authored Nov 03, 2018 by Joel Fernandes (Google) Committed by Kees Cook Dec 03, 2018

pstore/ram: Do not treat empty buffers as valid



The ramoops backend currently calls persistent_ram_save_old() even
if a buffer is empty. While this appears to work, it is does not seem
like the right thing to do and could lead to future bugs so lets avoid
that. It also prevents misleading prints in the logs which claim the
buffer is valid.

I got something like:

	found existing buffer, size 0, start 0

When I was expecting:

	no valid data in buffer (sig = ...)

This bails out early (and reports with pr_debug()), since it's an
acceptable state.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Co-developed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>

parent b05c9506

fs/pstore/ram_core.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -511,6 +511,11 @@ static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig,
		sig ^= PERSISTENT_RAM_SIG;

		if (prz->buffer->sig == sig) {
		if (buffer_size(prz) == 0) {
		pr_debug("found existing empty buffer\n");
		return 0;
		}

		if (buffer_size(prz) > prz->buffer_size \|\|
		buffer_start(prz) > buffer_size(prz)) {
		pr_info("found existing invalid buffer, size %zu, start %zu\n",