On 7/17/20 12:16 PM, Philippe Mathieu-Daudé wrote:
> libFuzzer found an undefined behavior (#DIV/0!) in ide_set_sector()
> when using a CD-ROM (reproducer available on the BugLink):
>
> UndefinedBehaviorSanitizer:DEADLYSIGNAL
> ==12163==ERROR: UndefinedBehaviorSanitizer: FPE on unknown address 0x5616279cffdc (pc 0x5616279cffdc bp 0x7ffcdaabae90 sp 0x7ffcdaabae30 T12163)
>
> Fix by initializing the CD-ROM number of sectors in ide_dev_initfn().
>
> Reported-by: Alexander Bulekov <alxndr@bu.edu>
> Fixes: b2df431407 ("ide scsi: Mess with geometry only for hard disk devices")
> BugLink: https://bugs.launchpad.net/qemu/+bug/1887309
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
> hw/ide/qdev.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/hw/ide/qdev.c b/hw/ide/qdev.c
> index 27ff1f7f66..6ce7fc317c 100644
> --- a/hw/ide/qdev.c
> +++ b/hw/ide/qdev.c
> @@ -201,6 +201,15 @@ static void ide_dev_initfn(IDEDevice *dev, IDEDriveKind kind, Error **errp)
> errp)) {
> return;
> }
> + } else {
> + uint64_t nb_sectors;
> +
> + blk_get_geometry(dev->conf.blk, &nb_sectors);
> + if (!nb_sectors) {
> + error_setg(errp, "CD-ROM size can not be zero");
Hmm this doesn't work because for some machines configure_blockdev()
creates blocks of zero size under your feet:
default_drive(default_cdrom, snapshot,
machine_class->block_default_type, 2,
CDROM_OPTS);
> + return;
> + }
> + dev->conf.secs = nb_sectors;
> }
> if (!blkconf_apply_backend_options(&dev->conf, kind == IDE_CD,
> kind != IDE_CD, errp)) {
>