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

[Emil Velikov]

On 27 February 2016 at 15:27, Gustavo Padovan
<gustavo.padovan@xxxxxxxxxxxxxxx> wrote:
> 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.
>
Up-to you really. I'm afraid that it doesn't resolve the issue :-(
As a test add a u64 value at the end of the struct and check the
output of pahole for 32 and 64 bit build.

>>
>> >  };
>> >
>> >  /**
>> > @@ -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.
>
Good point. Missed out the z in kzalloc :-)

-Emil