Re: [PATCH v4 5/5] staging/android: add flags member to sync ioctl structs

From: Gustavo Padovan
Date: Sat Feb 27 2016 - 10:28:09 EST


Hi Emil,

2016-02-27 Emil Velikov <emil.l.velikov@xxxxxxxxx>:

> Hi Gustavo,
>
> On 26 February 2016 at 18:31, Gustavo Padovan <gustavo@xxxxxxxxxxx> wrote:
> > From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
> >
> > Play safe and add flags member to all structs. So we don't need to
> > break API or create new IOCTL in the future if new features that requires
> > flags arises.
> >
> > v2: check if flags are valid (zero, in this case)
> >
> > Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
> > ---
> > drivers/staging/android/sync.c | 7 ++++++-
> > drivers/staging/android/uapi/sync.h | 6 ++++++
> > 2 files changed, 12 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/staging/android/sync.c b/drivers/staging/android/sync.c
> > index 837cff5..54fd5ab 100644
> > --- a/drivers/staging/android/sync.c
> > +++ b/drivers/staging/android/sync.c
> > @@ -445,6 +445,11 @@ static long sync_file_ioctl_merge(struct sync_file *sync_file,
> > goto err_put_fd;
> > }
> >
> > + if (data.flags) {
> > + err = -EFAULT;
> -EINVAL ?
>
> > + goto err_put_fd;
> > + }
> > +
> > fence2 = sync_file_fdget(data.fd2);
> > if (!fence2) {
> > err = -ENOENT;
> > @@ -511,7 +516,7 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
> > if (copy_from_user(&in, (void __user *)arg, sizeof(*info)))
> > return -EFAULT;
> >
> > - if (in.status || strcmp(in.name, "\0"))
> > + if (in.status || in.flags || strcmp(in.name, "\0"))
> > return -EFAULT;
> -EINVAL ?
>
> >
> > if (in.num_fences && !in.sync_fence_info)
> > diff --git a/drivers/staging/android/uapi/sync.h b/drivers/staging/android/uapi/sync.h
> > index 9aad623..f56a6c2 100644
> > --- a/drivers/staging/android/uapi/sync.h
> > +++ b/drivers/staging/android/uapi/sync.h
> > @@ -19,11 +19,13 @@
> > * @fd2: file descriptor of second fence
> > * @name: name of new fence
> > * @fence: returns the fd of the new fence to userspace
> > + * @flags: merge_data flags
> > */
> > struct sync_merge_data {
> > __s32 fd2;
> > char name[32];
> > __s32 fence;
> > + __u32 flags;
> The overall size of the struct is not multiple of 64bit, so things
> will end up badly if we decide to extend it in the future. Even if
> there's a small chance that update will be needed, we might as well
> pad it now (and check the padding for zero, returning -EINVAL).

I think name could be the first field here.

>
> > };
> >
> > /**
> > @@ -31,12 +33,14 @@ struct sync_merge_data {
> > * @obj_name: name of parent sync_timeline
> > * @driver_name: name of driver implementing the parent
> > * @status: status of the fence 0:active 1:signaled <0:error
> > + * @flags: fence_info flags
> > * @timestamp_ns: timestamp of status change in nanoseconds
> > */
> > struct sync_fence_info {
> > char obj_name[32];
> > char driver_name[32];
> > __s32 status;
> > + __u32 flags;
> > __u64 timestamp_ns;
> Should we be doing some form of validation in sync_fill_fence_info()
> of 'flags' ?

Do you think it is necessary? The kernel allocates a zero'ed buffer to
fill sync_fence_info array.

Gustavo