linux-kernel - [RFC 5/6] pstore: donot treat empty buffers as valid

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Date:   Fri, 26 Oct 2018 11:00:41 -0700
From:   "Joel Fernandes (Google)" <joel@...lfernandes.org>
To:     linux-kernel@...r.kernel.org
Cc:     kernel-team@...roid.com,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Kees Cook <keescook@...omium.org>,
        Tony Luck <tony.luck@...el.com>
Subject: [RFC 5/6] pstore: donot treat empty buffers as valid

pstore currently calls persistent_ram_save_old even if a buffer is
empty. While this appears to work, it is simply not the right thing to
do and could lead to bugs so lets avoid that. It also prevent misleading
prints in the logs which claim the buffer is valid.

Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
---
 fs/pstore/ram_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
index 0792595ebcfb..1299aa3ea734 100644
--- a/fs/pstore/ram_core.c
+++ b/fs/pstore/ram_core.c
@@ -495,7 +495,7 @@ static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig,
 
 	sig ^= PERSISTENT_RAM_SIG;
 
-	if (prz->buffer->sig == sig) {
+	if (prz->buffer->sig == sig && buffer_size(prz)) {
 		if (buffer_size(prz) > prz->buffer_size ||
 		    buffer_start(prz) > buffer_size(prz))
 			pr_info("found existing invalid buffer, size %zu, start %zu\n",
-- 
2.19.1.568.g152ad8e336-goog