relay: check array offset before using it

commit 9a29d0fbc2d9ad99fb8a981ab72548cc360e9d4c upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/relay.c b/kernel/relay.c
index da79a109dbeb..8f18d314a96a 100644
--- 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)