On Fri, Oct 09, 2015 at 04:13:45PM +0200, Arnd Bergmann wrote:
> 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.
Looks reasonable, thanks; applying for 4.4--b.
>
> Signed-off-by: Arnd Bergmann <a...@arndb.de>
> Fixes: c5e6aecd034e7 ("sunrpc: fix RCU handling of gc_ctx field")
>
> diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
> index dace13d7638e..799e65b944b9 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
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