On Tue, Jul 28, 2020 at 3:45 AM Peilin Ye <[email protected]> wrote: > > copy_one_buf() is copying uninitialized stack memory to userspace due to > the compiler not initializing holes in statically allocated structures. > Fix it by initializing `v` with memset().
I would add 'potentially' somewhere in that description: it is architecture dependent whether there are holes in this structure as 'enum' types and 'long' are both dependent on the ABI, and even if there is a hole, it is undefined behavior whether the hold gets initialized. Other than that, the patch looks good. > Cc: [email protected] > Fixes: 5c7640ab6258 ("switch compat_drm_infobufs() to drm_ioctl_kernel()") > Suggested-by: Dan Carpenter <[email protected]> > Signed-off-by: Peilin Ye <[email protected]> Acked-by: Arnd Bergmann <[email protected]> > --- > drivers/gpu/drm/drm_bufs.c | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/drm_bufs.c b/drivers/gpu/drm/drm_bufs.c > index a0735fbc144b..f99cd4a3f951 100644 > --- a/drivers/gpu/drm/drm_bufs.c > +++ b/drivers/gpu/drm/drm_bufs.c > @@ -1349,10 +1349,14 @@ static int copy_one_buf(void *data, int count, struct > drm_buf_entry *from) > { > struct drm_buf_info *request = data; > struct drm_buf_desc __user *to = &request->list[count]; > - struct drm_buf_desc v = {.count = from->buf_count, > - .size = from->buf_size, > - .low_mark = from->low_mark, > - .high_mark = from->high_mark}; > + struct drm_buf_desc v; > + > + memset(&v, 0, sizeof(v)); > + > + v.count = from->buf_count; > + v.size = from->buf_size; > + v.low_mark = from->low_mark; > + v.high_mark = from->high_mark; > > if (copy_to_user(to, &v, offsetof(struct drm_buf_desc, flags))) > return -EFAULT; > -- > 2.25.1 >
