[Qemu-stable] [PATCH 16/25] scsi: pvscsi: limit process IO loop to ring size

[Michael Roth]

From: Prasad J Pandit <address@hidden>

Vmware Paravirtual SCSI emulator while processing IO requests
could run into an infinite loop if 'pvscsi_ring_pop_req_descr'
always returned positive value. Limit IO loop to the ring size.

Cc: address@hidden
Reported-by: Li Qiang <address@hidden>
Signed-off-by: Prasad J Pandit <address@hidden>
Message-Id: <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
(cherry picked from commit d251157ac1928191af851d199a9ff255d330bec9)
Signed-off-by: Michael Roth <address@hidden>
---
 hw/scsi/vmw_pvscsi.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/hw/scsi/vmw_pvscsi.c b/hw/scsi/vmw_pvscsi.c
index 2d7528d..fe74d86 100644
--- a/hw/scsi/vmw_pvscsi.c
+++ b/hw/scsi/vmw_pvscsi.c
@@ -252,8 +252,11 @@ static hwaddr
 pvscsi_ring_pop_req_descr(PVSCSIRingInfo *mgr)
 {
     uint32_t ready_ptr = RS_GET_FIELD(mgr, reqProdIdx);
+    uint32_t ring_size = PVSCSI_MAX_NUM_PAGES_REQ_RING
+                            * PVSCSI_MAX_NUM_REQ_ENTRIES_PER_PAGE;
 
-    if (ready_ptr != mgr->consumed_ptr) {
+    if (ready_ptr != mgr->consumed_ptr
+        && ready_ptr - mgr->consumed_ptr < ring_size) {
         uint32_t next_ready_ptr =
             mgr->consumed_ptr++ & mgr->txr_len_mask;
         uint32_t next_ready_page =
-- 
1.9.1