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That's all we know. X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Ruhr-University , John Snow , QEMU Developers , qemu-block@nongnu.org, Prasad J Pandit Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" P J P =E4=BA=8E2020=E5=B9=B48=E6=9C=8827=E6=97=A5=E5= =91=A8=E5=9B=9B =E4=B8=8B=E5=8D=887:41=E5=86=99=E9=81=93=EF=BC=9A > > From: Prasad J Pandit > > While transferring data via fdctrl_write_data(), 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_nul= lptr1 > =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 > --- > hw/block/fdc.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/hw/block/fdc.c b/hw/block/fdc.c > index e9ed3eef45..dedadac68a 100644 > --- a/hw/block/fdc.c > +++ b/hw/block/fdc.c > @@ -2419,7 +2419,8 @@ static void fdctrl_write_data(FDCtrl *fdctrl, uint3= 2_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->fif= o, > + if (cur_drv->blk > + && blk_pwrite(cur_drv->blk, fd_offset(cur_drv), fdctrl->= fifo, > BDRV_SECTOR_SIZE, 0) < 0) { > FLOPPY_DPRINTF("error writing sector %d\n", > fd_sector(cur_drv)); > -- Hello Prasad, There are several pattern to address this NULL check in fdc.c. I think it is better to consider this as an error. Just like the check in 'fdctrl_format_sector': if (cur_drv->blk =3D=3D NULL || blk_pwrite(cur_drv->blk, fd_offset(cur_drv), fdctrl->fifo, BDRV_SECTOR_SIZE, 0) < 0) { FLOPPY_DPRINTF("error formatting sector %d\n", fd_sector(cur_drv)); fdctrl_stop_transfer(fdctrl, FD_SR0_ABNTERM | FD_SR0_SEEK, 0x00, 0x00); } else { Also there seems exists the same issue in 'fdctrl_read_data' Thanks, Li Qiang > 2.26.2 > >