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Subject[PATCH 4.2.y-ckt 149/211] sunrpc: avoid warning in gss_key_timeout
Date
4.2.8-ckt1 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Arnd Bergmann <arnd@arndb.de>

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@arndb.de>
Fixes: c5e6aecd034e7 ("sunrpc: fix RCU handling of gc_ctx field")
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Kamal Mostafa <kamal@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


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