rapidio/tsi721: fix queue wrapping bug in inbound doorbell handler

Fix a bug that causes a kernel panic when the number of received doorbells
is larger than number of entries in the inbound doorbell queue (current
default value = 512).

Another possible indication for this bug is large number of spurious
doorbells reported by tsi721 driver after reaching the queue size maximum.

Signed-off-by: Alexandre Bounine <alexandre.bounine@idt.com>
Cc: Chul Kim <chul.kim@idt.com>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: <stable@vger.kernel.org>		[3.2.x+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/rapidio/devices/tsi721.c b/drivers/rapidio/devices/tsi721.c
index 691b1ab1a3d0..30d2072f480b 100644
--- a/drivers/rapidio/devices/tsi721.c
+++ b/drivers/rapidio/devices/tsi721.c
@@ -410,13 +410,14 @@ static void tsi721_db_dpc(struct work_struct *work)
          */
         mport = priv->mport;
 
-        wr_ptr = ioread32(priv->regs + TSI721_IDQ_WP(IDB_QUEUE));
-        rd_ptr = ioread32(priv->regs + TSI721_IDQ_RP(IDB_QUEUE));
+        wr_ptr = ioread32(priv->regs + TSI721_IDQ_WP(IDB_QUEUE)) % IDB_QSIZE;
+        rd_ptr = ioread32(priv->regs + TSI721_IDQ_RP(IDB_QUEUE)) % IDB_QSIZE;
 
         while (wr_ptr != rd_ptr) {
                 idb_entry = (u64 *)(priv->idb_base +
                                         (TSI721_IDB_ENTRY_SIZE * rd_ptr));
                 rd_ptr++;
+                rd_ptr %= IDB_QSIZE;
                 idb.msg = *idb_entry;
                 *idb_entry = 0;