diff options
Diffstat (limited to 'hw')
| -rw-r--r-- | hw/block/fdc.c | 23 |
1 files changed, 20 insertions, 3 deletions
diff --git a/hw/block/fdc.c b/hw/block/fdc.c index fa933cd326..21d18ac2e3 100644 --- a/hw/block/fdc.c +++ b/hw/block/fdc.c @@ -61,6 +61,12 @@ } while (0) +/* Anonymous BlockBackend for empty drive */ +static BlockBackend *blk_create_empty_drive(void) +{ + return blk_new(qemu_get_aio_context(), 0, BLK_PERM_ALL); +} + /********************************************************/ /* qdev floppy bus */ @@ -486,8 +492,7 @@ static void floppy_drive_realize(DeviceState *qdev, Error **errp) } if (!dev->conf.blk) { - /* Anonymous BlockBackend for an empty drive */ - dev->conf.blk = blk_new(qemu_get_aio_context(), 0, BLK_PERM_ALL); + dev->conf.blk = blk_create_empty_drive(); ret = blk_attach_dev(dev->conf.blk, qdev); assert(ret == 0); @@ -1161,7 +1166,19 @@ static FDrive *get_drv(FDCtrl *fdctrl, int unit) static FDrive *get_cur_drv(FDCtrl *fdctrl) { - return get_drv(fdctrl, fdctrl->cur_drv); + FDrive *cur_drv = get_drv(fdctrl, fdctrl->cur_drv); + + if (!cur_drv->blk) { + /* + * Kludge: empty drive line selected. Create an anonymous + * BlockBackend to avoid NULL deref with various BlockBackend + * API calls within this model (CVE-2021-20196). + * Due to the controller QOM model limitations, we don't + * attach the created to the controller device. + */ + cur_drv->blk = blk_create_empty_drive(); + } + return cur_drv; } /* Status A register : 0x00 (read-only) */ |