On Wed, Sep 28, 2022 at 01:19:21PM -0700, Nathan Chancellor wrote: > When building s390 allmodconfig after commit 9b91a6523078 ("usb: gadget: > uvc: increase worker prio to WQ_HIGHPRI"), the following error occurs: > > In file included from ../include/linux/string.h:253, > from ../include/linux/bitmap.h:11, > from ../include/linux/cpumask.h:12, > from ../include/linux/smp.h:13, > from ../include/linux/lockdep.h:14, > from ../include/linux/rcupdate.h:29, > from ../include/linux/rculist.h:11, > from ../include/linux/pid.h:5, > from ../include/linux/sched.h:14, > from ../include/linux/ratelimit.h:6, > from ../include/linux/dev_printk.h:16, > from ../include/linux/device.h:15, > from ../drivers/usb/gadget/function/f_uvc.c:9: > In function ‘fortify_memset_chk’, > inlined from ‘uvc_register_video’ at ../drivers/usb/gadget/function/f_uvc.c:424:2: > ../include/linux/fortify-string.h:301:25: error: call to ‘__write_overflow_field’ declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning] > 301 | __write_overflow_field(p_size_field, size); > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > This points to the memset() in uvc_register_video(). It is clear that > the argument to sizeof() is incorrect, as uvc->vdev (a 'struct > video_device') is being zeroed out but the size of uvc->video (a 'struct > uvc_video') is being used as the third arugment to memset(). > > pahole shows that prior to commit 9b91a6523078 ("usb: gadget: uvc: > increase worker prio to WQ_HIGHPRI"), 'struct video_device' and > 'struct ucv_video' had the same size, meaning that the argument to > sizeof() is incorrect semantically but there is no visible issue: > > $ pahole -s build/drivers/usb/gadget/function/f_uvc.o | grep -E "(uvc_video|video_device)\s+" > video_device 1400 4 > uvc_video 1400 3 > > After that change, uvc_video becomes slightly larger, meaning that the > memset() will overwrite by 8 bytes: > > $ pahole -s build/drivers/usb/gadget/function/f_uvc.o | grep -E "(uvc_video|video_device)\s+" > video_device 1400 4 > uvc_video 1408 3 > > Fix the arugment to sizeof() so that there is no overwrite. > > Cc: stable@xxxxxxxxxxxxxxx > Fixes: e4ce9ed835bc ("usb: gadget: uvc: ensure the vdev is unset") > Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx> Thanks for tracking that down! Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> -- Kees Cook