relay: check array offset before using it

Smatch complains that we started using the array offset before we
checked that it was valid.

Fixes: 017c59c042d0 ('relay: Use per CPU constructs for the relay channel buffer pointers')
Link: http://lkml.kernel.org/r/20161013084947.GC16198@mwanda
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/relay.c b/kernel/relay.c
index da79a109dbebc6f7d4cf725182b05365a946614b..8f18d314a96a49a1e9fc6c4cf1c5bead5c96a787 100644 (file)
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -809,11 +809,11 @@ void relay_subbufs_consumed(struct rchan *chan,
 {
        struct rchan_buf *buf;
 
-       if (!chan)
+       if (!chan || cpu >= NR_CPUS)
                return;
 
        buf = *per_cpu_ptr(chan->buf, cpu);
-       if (cpu >= NR_CPUS || !buf || subbufs_consumed > chan->n_subbufs)
+       if (!buf || subbufs_consumed > chan->n_subbufs)
                return;
 
        if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)