File CVE-2016-1568-qemuu-ide-ahci-reset-ncq-object-to-unused-on-error.patch of Package xen.4507

Reference: bsc#961332 CVE-2016-1568

From: Prasad J Pandit <address@hidden>

When processing NCQ commands, ACHI device emulation prepares a
NCQ transfer object; To which an aio control block(aiocb) object
is assigned in 'execute_ncq_command'. In case, when the NCQ
command is invalid, the 'aiocb' object is not assigned, and NCQ
transfer object is left as 'used'. This leads to a use after
free kind of error in 'bdrv_aio_cancel_async' via 'ahci_reset_port'.
Reset NCQ transfer object to 'unused' to avoid it.

Reported-by: Qinghao Tang <address@hidden>
Signed-off-by: Prasad J Pandit <address@hidden>
---
 hw/ide/ahci.c | 1 +
 1 file changed, 1 insertion(+)

Update as per review in
  -> https://lists.gnu.org/archive/html/qemu-devel/2016-01/msg01175.html

Index: xen-4.4.3-testing/tools/qemu-xen-dir-remote/hw/ide/ahci.c
===================================================================
--- xen-4.4.3-testing.orig/tools/qemu-xen-dir-remote/hw/ide/ahci.c
+++ xen-4.4.3-testing/tools/qemu-xen-dir-remote/hw/ide/ahci.c
@@ -773,7 +773,10 @@ static void process_ncq_command(AHCIStat
             ncq_tfs->lba, ncq_tfs->lba + ncq_tfs->sector_count - 2,
             s->dev[port].port.ifs[0].nb_sectors - 1);
 
-    ahci_populate_sglist(&s->dev[port], &ncq_tfs->sglist, 0);
+    if (ahci_populate_sglist(&s->dev[port], &ncq_tfs->sglist, 0) == -1) {
+        ncq_tfs->used = 0;
+        return;
+    }
     ncq_tfs->tag = tag;
 
     switch(ncq_fis->command) {
@@ -807,6 +810,7 @@ static void process_ncq_command(AHCIStat
         default:
             DPRINTF(port, "error: tried to process non-NCQ command as NCQ\n");
             qemu_sglist_destroy(&ncq_tfs->sglist);
+            ncq_tfs->used = 0;
             break;
     }
 }