Previously the guest controlled the value of last_sec and wasn't particularly careful to check it didn't exceed the media size. We can't re-use drv->last_sec as that changes as we do operations so we set media_last_sect when the geometry is probed. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/3800 Signed-off-by: Alex Bennée <alex.bennee@linaro.org> --- v2 - checkpatch --- hw/block/fdc-internal.h | 1 + hw/block/fdc.c | 28 ++++++++++++++++++++++------ 2 files changed, 23 insertions(+), 6 deletions(-) diff --git a/hw/block/fdc-internal.h b/hw/block/fdc-internal.h index e219623dc7a..3a39ac903c7 100644 --- a/hw/block/fdc-internal.h +++ b/hw/block/fdc-internal.h @@ -83,6 +83,7 @@ typedef struct FDrive { uint8_t max_track; /* Nb of tracks */ uint16_t bps; /* Bytes per sector */ uint8_t ro; /* Is read-only */ + uint8_t media_last_sect; /* Probed sector per track*/ uint8_t media_changed; /* Is media changed */ uint8_t media_rate; /* Data rate of medium */ diff --git a/hw/block/fdc.c b/hw/block/fdc.c index 1178b959a64..18a61f5ce87 100644 --- a/hw/block/fdc.c +++ b/hw/block/fdc.c @@ -192,6 +192,7 @@ static void fd_init(FDrive *drv) drv->max_track = 0; drv->ro = true; drv->media_changed = 1; + drv->media_last_sect = 0; } #define NUM_SIDES(drv) ((drv)->flags & FDISK_DBL_SIDES ? 2 : 1) @@ -373,6 +374,7 @@ static int pick_geometry(FDrive *drv) } drv->max_track = parse->max_track; drv->last_sect = parse->last_sect; + drv->media_last_sect = parse->last_sect; drv->disk = parse->drive; drv->media_rate = parse->rate; return 0; @@ -1905,6 +1907,17 @@ static void fdctrl_handle_partid(FDCtrl *fdctrl, int direction) fdctrl_to_result_phase(fdctrl, 1); } +static bool fd_validate_last_sect(FDrive *drv, uint8_t new_last_sect_val) +{ + if (drv->media_validated && new_last_sect_val > drv->media_last_sect) { + qemu_log_mask(LOG_GUEST_ERROR, + "FDC: Guest attempted to set last_sect to %u, exceeding valid media max of %u\n", + new_last_sect_val, drv->media_last_sect); + return false; + } + return true; +} + static void fdctrl_handle_restore(FDCtrl *fdctrl, int direction) { FDrive *cur_drv = get_cur_drv(fdctrl); @@ -1919,6 +1932,10 @@ static void fdctrl_handle_restore(FDCtrl *fdctrl, int direction) /* timers */ fdctrl->timer0 = fdctrl->fifo[7]; fdctrl->timer1 = fdctrl->fifo[8]; + if (!fd_validate_last_sect(cur_drv, fdctrl->fifo[9])) { + fdctrl_stop_transfer(fdctrl, FD_SR0_ABNTERM, FD_SR1_EC, 0x00); + return; + } cur_drv->last_sect = fdctrl->fifo[9]; fdctrl->lock = fdctrl->fifo[10] >> 7; cur_drv->perpendicular = (fdctrl->fifo[10] >> 2) & 0xF; @@ -1983,13 +2000,12 @@ static void fdctrl_handle_format_track(FDCtrl *fdctrl, int direction) fdctrl->data_state &= ~FD_STATE_MULTI; cur_drv->bps = fdctrl->fifo[2] > 7 ? 16384 : 128 << fdctrl->fifo[2]; -#if 0 - cur_drv->last_sect = - cur_drv->flags & FDISK_DBL_SIDES ? fdctrl->fifo[3] : - fdctrl->fifo[3] / 2; -#else + + if (!fd_validate_last_sect(cur_drv, fdctrl->fifo[3])) { + fdctrl_stop_transfer(fdctrl, FD_SR0_ABNTERM, FD_SR1_EC, 0x00); + return; + } cur_drv->last_sect = fdctrl->fifo[3]; -#endif /* TODO: implement format using DMA expected by the Bochs BIOS * and Linux fdformat (read 3 bytes per sector via DMA and fill * the sector with the specified fill byte -- 2.47.3