From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1LSaAR-0003MO-Jg for qemu-devel@nongnu.org; Thu, 29 Jan 2009 11:55:03 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1LSaAQ-0003LX-6G for qemu-devel@nongnu.org; Thu, 29 Jan 2009 11:55:03 -0500 Received: from [199.232.76.173] (port=34571 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LSaAQ-0003LQ-1x for qemu-devel@nongnu.org; Thu, 29 Jan 2009 11:55:02 -0500 Received: from mx2.redhat.com ([66.187.237.31]:39136) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1LSaAP-0004pK-EG for qemu-devel@nongnu.org; Thu, 29 Jan 2009 11:55:01 -0500 Received: from int-mx2.corp.redhat.com (int-mx2.corp.redhat.com [172.16.27.26]) by mx2.redhat.com (8.13.8/8.13.8) with ESMTP id n0TGt0Vo009146 for ; Thu, 29 Jan 2009 11:55:00 -0500 Date: Thu, 29 Jan 2009 11:54:56 -0500 From: Rik van Riel Message-ID: <20090129115456.2593238b@bree.surriel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] [PATCH] check SCSI read/write requests against max LBA Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org The bdrv layer uses a signed offset. Furthermore, block-raw-posix only seeks when that offset is positive. Passing a negative offset to block-raw-posix can result in data being written at the current seek cursor's position. It may be possible to exploit this to seek to the end of the disk and extend the virtual disk by writing data to a negative sector offset. After a reboot, this could lead to the guest having a larger disk than it had before. Close the hole by sanity checking the lba against the size of the disk. Signed-off-by: Rik van Riel Index: qemu/hw/scsi-disk.c =================================================================== --- qemu.orig/hw/scsi-disk.c +++ qemu/hw/scsi-disk.c @@ -67,6 +67,7 @@ struct SCSIDeviceState /* The qemu block layer uses a fixed 512 byte sector size. This is the number of 512 byte blocks in a single scsi sector. */ int cluster_size; + uint64_t max_lba; int sense; int tcq; /* Completion functions may be called from either scsi_{read,write}_data @@ -738,6 +739,8 @@ static int32_t scsi_send_command(SCSIDev /* Returned value is the address of the last sector. */ if (nb_sectors) { nb_sectors--; + /* Remember the new size for read/write sanity checking. */ + s->max_lba = nb_sectors; /* Clip to 2TB, instead of returning capacity modulo 2TB. */ if (nb_sectors > UINT32_MAX) nb_sectors = UINT32_MAX; @@ -759,6 +762,8 @@ static int32_t scsi_send_command(SCSIDev case 0x28: case 0x88: DPRINTF("Read (sector %lld, count %d)\n", lba, len); + if (lba > s->max_lba) + goto illegal_lba; r->sector = lba * s->cluster_size; r->sector_count = len * s->cluster_size; break; @@ -766,6 +771,8 @@ static int32_t scsi_send_command(SCSIDev case 0x2a: case 0x8a: DPRINTF("Write (sector %lld, count %d)\n", lba, len); + if (lba > s->max_lba) + goto illegal_lba; r->sector = lba * s->cluster_size; r->sector_count = len * s->cluster_size; is_write = 1; @@ -839,6 +847,8 @@ static int32_t scsi_send_command(SCSIDev /* Returned value is the address of the last sector. */ if (nb_sectors) { nb_sectors--; + /* Remember the new size for read/write sanity checking. */ + s->max_lba = nb_sectors; outbuf[0] = (nb_sectors >> 56) & 0xff; outbuf[1] = (nb_sectors >> 48) & 0xff; outbuf[2] = (nb_sectors >> 40) & 0xff; @@ -877,6 +887,9 @@ static int32_t scsi_send_command(SCSIDev fail: scsi_command_complete(r, STATUS_CHECK_CONDITION, SENSE_ILLEGAL_REQUEST); return 0; + illegal_lba: + scsi_command_complete(r, STATUS_CHECK_CONDITION, SENSE_HARDWARE_ERROR); + return 0; } if (r->sector_count == 0 && r->buf_len == 0) { scsi_command_complete(r, STATUS_GOOD, SENSE_NO_SENSE); @@ -902,6 +915,7 @@ SCSIDevice *scsi_disk_init(BlockDriverSt { SCSIDevice *d; SCSIDeviceState *s; + uint64_t nb_sectors; s = (SCSIDeviceState *)qemu_mallocz(sizeof(SCSIDeviceState)); s->bdrv = bdrv; @@ -913,6 +927,11 @@ SCSIDevice *scsi_disk_init(BlockDriverSt } else { s->cluster_size = 1; } + bdrv_get_geometry(s->bdrv, &nb_sectors); + nb_sectors /= s->cluster_size; + if (nb_sectors) + nb_sectors--; + s->max_lba = nb_sectors; strncpy(s->drive_serial_str, drive_get_serial(s->bdrv), sizeof(s->drive_serial_str)); if (strlen(s->drive_serial_str) == 0)