Reference: bsc#961332 CVE-2016-1568 From: Prasad J Pandit 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 Signed-off-by: Prasad J Pandit --- 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-4.6.0-testing/tools/qemu-xen-dir-remote/hw/ide/ahci.c =================================================================== --- xen-4.6.0-testing.orig/tools/qemu-xen-dir-remote/hw/ide/ahci.c +++ xen-4.6.0-testing/tools/qemu-xen-dir-remote/hw/ide/ahci.c @@ -902,7 +902,10 @@ 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) { @@ -943,6 +946,7 @@ static void process_ncq_command(AHCIStat "error: tried to process non-NCQ command as NCQ\n"); } qemu_sglist_destroy(&ncq_tfs->sglist); + ncq_tfs->used = 0; } }