linux-kernel - [PATCH RFC v2 3/3] pstore: donot treat empty buffers as valid

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Message-Id: <20181103233818.44615-4-joel@joelfernandes.org>
Date:   Sat,  3 Nov 2018 16:38:18 -0700
From:   "Joel Fernandes (Google)" <joel@...lfernandes.org>
To:     linux-kernel@...r.kernel.org
Cc:     "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: [PATCH RFC v2 3/3] 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 does not seem like the right
thing to do and could lead to future bugs so lets avoid that. It also
prevent 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 = ...)

Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
---
Note that if you feel this patch is not necessary, then feel free to
drop it. I would say it is harmless and is a good clean up.

 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 e6375439c5ac..196e4fd7ba8c 100644
--- a/fs/pstore/ram_core.c
+++ b/fs/pstore/ram_core.c
@@ -510,7 +510,7 @@ 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",
-- 
2.19.1.930.g4563a0d9d0-goog