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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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