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charset="utf-8" From: Prasad J Pandit While transferring data via fdctrl_read/write_data() routines, check that current drive does not have a null block pointer. Avoid null pointer dereference. -> https://ruhr-uni-bochum.sciebo.de/s/NNWP2GfwzYKeKwE?path=3D%2Ffdc_nullp= tr1 =3D=3D1658854=3D=3DHint: address points to the zero page. #0 blk_inc_in_flight block/block-backend.c:1327 #1 blk_prw block/block-backend.c:1299 #2 blk_pwrite block/block-backend.c:1464 #3 fdctrl_write_data hw/block/fdc.c:2418 #4 fdctrl_write hw/block/fdc.c:962 #5 portio_write ioport.c:205 #6 memory_region_write_accessor memory.c:483 #7 access_with_adjusted_size memory.c:544 #8 memory_region_dispatch_write memory.c:1476 Reported-by: Ruhr-University Signed-off-by: Prasad J Pandit Reviewed-by: Li Qiang --- hw/block/fdc.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) Update v2: treat NULL blk pointer as an error -> https://lists.nongnu.org/archive/html/qemu-devel/2020-09/msg06642.html diff --git a/hw/block/fdc.c b/hw/block/fdc.c index 224bac504f..bf968dc66f 100644 --- a/hw/block/fdc.c +++ b/hw/block/fdc.c @@ -1923,7 +1923,8 @@ static uint32_t fdctrl_read_data(FDCtrl *fdctrl) fd_sector(cur_drv)); return 0; } - if (blk_pread(cur_drv->blk, fd_offset(cur_drv), fdctrl->fifo, + if (!cur_drv->blk + || blk_pread(cur_drv->blk, fd_offset(cur_drv), fdctrl->fif= o, BDRV_SECTOR_SIZE) < 0) { FLOPPY_DPRINTF("error getting sector %d\n", @@ -2427,7 +2428,8 @@ static void fdctrl_write_data(FDCtrl *fdctrl, uint32_= t value) if (pos =3D=3D FD_SECTOR_LEN - 1 || fdctrl->data_pos =3D=3D fdctrl->data_len) { cur_drv =3D get_cur_drv(fdctrl); - if (blk_pwrite(cur_drv->blk, fd_offset(cur_drv), fdctrl->fifo, + if (!cur_drv->blk + || blk_pwrite(cur_drv->blk, fd_offset(cur_drv), fdctrl->fi= fo, BDRV_SECTOR_SIZE, 0) < 0) { FLOPPY_DPRINTF("error writing sector %d\n", fd_sector(cur_drv)); -- 2.26.2