linux-kernel - [PATCH] pstore/ram: no timekeeping calls when unavailable

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Message-ID: <20121105210421.GA14819@www.outflux.net>
Date:	Mon, 5 Nov 2012 13:04:21 -0800
From:	Kees Cook <keescook@...omium.org>
To:	linux-kernel@...r.kernel.org
Cc:	Anton Vorontsov <cbouatmailru@...il.com>,
	Colin Cross <ccross@...roid.com>,
	Kees Cook <keescook@...omium.org>,
	Doug Anderson <dianders@...omium.org>,
	Tony Luck <tony.luck@...el.com>
Subject: [PATCH] pstore/ram: no timekeeping calls when unavailable

We must not call timekeeping functions unless they are available. If we dump
before they have resumed, avoid a WARN_ON by setting the timestamp to 0.

Reported-by: Doug Anderson <dianders@...omium.org>
Cc: Anton Vorontsov <cbouatmailru@...il.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 fs/pstore/ram.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 1a4f6da..6d014e0 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -171,7 +171,13 @@ static size_t ramoops_write_kmsg_hdr(struct persistent_ram_zone *prz)
 	struct timeval timestamp;
 	size_t len;
 
-	do_gettimeofday(&timestamp);
+	/* Handle dumping before timekeeping has resumed. */
+	if (unlikely(timekeeping_suspended)) {
+		timestamp.tv_sec = 0;
+		timestamp.tv_usec = 0;
+	} else
+		do_gettimeofday(&timestamp);
+
 	hdr = kasprintf(GFP_ATOMIC, RAMOOPS_KERNMSG_HDR "%lu.%lu\n",
 		(long)timestamp.tv_sec, (long)timestamp.tv_usec);
 	WARN_ON_ONCE(!hdr);
-- 
1.7.9.5


-- 
Kees Cook
Chrome OS Security
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