[4.2.y-ckt stable] Patch "sunrpc: avoid warning in gss_key_timeout" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    sunrpc: avoid warning in gss_key_timeout

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt1.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 4e31a5b7db5fc1906adf030aea6039b981b81c58 Mon Sep 17 00:00:00 2001
From: Arnd Bergmann <arnd at arndb.de>
Date: Fri, 9 Oct 2015 16:13:45 +0200
Subject: sunrpc: avoid warning in gss_key_timeout

commit cc6a7aab5570beef884ff95f7cade6634bf815a1 upstream.

The gss_key_timeout() function causes a harmless warning in some
configurations, e.g. ARM imx_v6_v7_defconfig with gcc-5.2, if the
compiler cannot figure out the state of the 'expire' variable across
an rcu_read_unlock():

net/sunrpc/auth_gss/auth_gss.c: In function 'gss_key_timeout':
net/sunrpc/auth_gss/auth_gss.c:1422:211: warning: 'expire' may be used uninitialized in this function [-Wmaybe-uninitialized]

To avoid this warning without adding a bogus initialization, this
rewrites the function so the comparison is done inside of the
critical section. As a side-effect, it also becomes slightly
easier to understand because the implementation now more closely
resembles the comment above it.

Signed-off-by: Arnd Bergmann <arnd at arndb.de>
Fixes: c5e6aecd034e7 ("sunrpc: fix RCU handling of gc_ctx field")
Signed-off-by: J. Bruce Fields <bfields at redhat.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/sunrpc/auth_gss/auth_gss.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
index dace13d..799e65b 100644
--- a/net/sunrpc/auth_gss/auth_gss.c
+++ b/net/sunrpc/auth_gss/auth_gss.c
@@ -1411,17 +1411,16 @@ gss_key_timeout(struct rpc_cred *rc)
 {
 	struct gss_cred *gss_cred = container_of(rc, struct gss_cred, gc_base);
 	struct gss_cl_ctx *ctx;
-	unsigned long now = jiffies;
-	unsigned long expire;
+	unsigned long timeout = jiffies + (gss_key_expire_timeo * HZ);
+	int ret = 0;

 	rcu_read_lock();
 	ctx = rcu_dereference(gss_cred->gc_ctx);
-	if (ctx)
-		expire = ctx->gc_expiry - (gss_key_expire_timeo * HZ);
+	if (!ctx || time_after(timeout, ctx->gc_expiry))
+		ret = -EACCES;
 	rcu_read_unlock();
-	if (!ctx || time_after(now, expire))
-		return -EACCES;
-	return 0;
+
+	return ret;
 }

 static int
--
1.9.1