Re: [Linux-kernel-mentees] [PATCH v3] media/v4l2-core: Fix kernel-infoleak in video_put_user()

[Dan Carpenter]

On Mon, Jul 27, 2020 at 09:25:16AM +0200, Arnd Bergmann wrote:
> On Mon, Jul 27, 2020 at 12:28 AM Peilin Ye <yepeilin.cs@xxxxxxxxx> wrote:
> >
> > video_put_user() is copying uninitialized stack memory to userspace due
> > to the compiler not initializing holes in the structures declared on the
> > stack. Fix it by initializing `ev32` and `vb32` using memset().
> >
> > Reported-and-tested-by: syzbot+79d751604cb6f29fbf59@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Link: https://syzkaller.appspot.com/bug?extid=79d751604cb6f29fbf59
> > Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > Signed-off-by: Peilin Ye <yepeilin.cs@xxxxxxxxx>
> 
> Thanks a lot for addressing this! I now see that I actually created a similar
> bugfix for it back in January, but for some reason that got stuck in my
> backlog and I never wrote a proper description for it or sent it out to the
> list, sorry about that. I would hope we could find a way to have either
> the compiler or sparse warn if we copy uninitialized data to user space,
> but we now don't even check for that within the kernel any more.

Here are my latest warnings on linux-next from Friday.

block/scsi_ioctl.c:707 scsi_put_cdrom_generic_arg() warn: check that 'cgc32' doesn't leak information (struct has a hole after 'data_direction')
drivers/input/misc/uinput.c:743 uinput_ff_upload_to_user() warn: check that 'ff_up_compat' doesn't leak information (struct has a hole after 'replay')
drivers/input/misc/uinput.c:958 uinput_ioctl_handler() warn: check that 'ff_up' doesn't leak information (struct has a hole after 'replay')
drivers/firewire/core-cdev.c:463 ioctl_get_info() warn: check that 'bus_reset' doesn't leak information (struct has a hole after 'generation')
drivers/scsi/megaraid/megaraid_mm.c:824 kioc_to_mimd() warn: check that 'cinfo.base' doesn't leak information
drivers/gpio/gpiolib-cdev.c:473 lineevent_read() warn: check that 'ge' doesn't leak information (struct has a hole after 'id')
drivers/gpu/drm/i915/i915_query.c:136 query_engine_info() warn: check that 'query.num_engines' doesn't leak information
drivers/gpu/drm/drm_bufs.c:1357 copy_one_buf() warn: check that 'v' doesn't leak information (struct has a hole after 'flags')
drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c:785 amdgpu_info_ioctl() warn: check that 'dev_info' doesn't leak information (struct has a hole after 'pa_sc_tile_steering_override')
drivers/block/floppy.c:3132 raw_cmd_copyout() warn: check that 'cmd' doesn't leak information (struct has a hole after 'flags')
drivers/char/hpet.c:675 hpet_ioctl() warn: check that 'info' doesn't leak information (struct has a hole after 'hi_timer')
drivers/media/v4l2-core/v4l2-ioctl.c:3204 video_put_user() warn: check that 'ev32' doesn't leak information (struct has a hole after 'type')
drivers/media/v4l2-core/v4l2-ioctl.c:3229 video_put_user() warn: check that 'vb32' doesn't leak information (struct has a hole after 'memory')
drivers/net/wan/sbni.c:1320 sbni_ioctl() warn: check that 'flags' doesn't leak information (struct has a hole after 'rxl')
drivers/infiniband/hw/qedr/verbs.c:1816 qedr_create_user_qp() warn: check that 'uresp' doesn't leak information (struct has a hole after 'sq_icid')
drivers/infiniband/hw/cxgb4/provider.c:107 c4iw_alloc_ucontext() warn: check that 'uresp.reserved' doesn't leak information
drivers/tty/vt/vt_ioctl.c:1218 vt_compat_ioctl() warn: check that 'op' doesn't leak information (struct has a hole after 'charcount')
net/smc/smc_diag.c:181 __smc_diag_dump() warn: check that 'dinfo' doesn't leak information (struct has a hole after 'linkid')
net/sched/act_ife.c:638 tcf_ife_dump() warn: check that 'opt' doesn't leak information (struct has a hole after 'flags')
net/sched/act_skbmod.c:232 tcf_skbmod_dump() warn: check that 'opt' doesn't leak information (struct has a hole after 'bindcnt')
net/sched/act_connmark.c:187 tcf_connmark_dump() warn: check that 'opt' doesn't leak information (struct has a hole after 'zone')
net/openvswitch/conntrack.c:311 ovs_ct_put_key() warn: check that 'orig' doesn't leak information (struct has a hole after 'ipv4_proto')
net/openvswitch/conntrack.c:322 ovs_ct_put_key() warn: check that 'orig' doesn't leak information (struct has a hole after 'ipv6_proto')
net/rds/recv.c:492 rds_notify_queue_get() warn: check that 'cmsg' doesn't leak information (struct has a hole after 'status')
net/xdp/xsk.c:870 xsk_getsockopt() warn: check that 'stats.rx_ring_full' doesn't leak information
kernel/signal.c:3524 __do_sys_rt_sigtimedwait() warn: check that 'info' doesn't leak information (struct has a hole after 'si_code')
kernel/signal.c:3524 __do_sys_rt_sigtimedwait() warn: check that 'info' doesn't leak information (struct has a hole after 'si_code')
kernel/signal.c:3556 __do_sys_rt_sigtimedwait_time32() warn: check that 'info' doesn't leak information (struct has a hole after 'si_code')
kernel/signal.c:3556 __do_sys_rt_sigtimedwait_time32() warn: check that 'info' doesn't leak information (struct has a hole after 'si_code')
kernel/signal.c:4055 __do_sys_sigaltstack() warn: check that 'old' doesn't leak information (struct has a hole after 'ss_flags')
kernel/signal.c:4055 __do_sys_sigaltstack() warn: check that 'old' doesn't leak information (struct has a hole after 'ss_flags')
kernel/ptrace.c:998 ptrace_get_syscall_info() warn: check that 'info' doesn't leak information (struct has a hole after 'op')

regards,
dan carpenter