On 11/03, Chao Yu wrote:
> On 2020/11/3 11:22, Eric Biggers wrote:
> > On Mon, Nov 02, 2020 at 02:21:31PM +0800, Chao Yu wrote:
> > > +#define F2FS_IOC_MOVE_RANGE _IOWR(F2FS_IOCTL_MAGIC, 9,
> > > \
> > > + struct f2fs_move_range)
> > [...]
> > > +#define F2FS_IOC_GARBAGE_COLLECT_RANGE _IOW(F2FS_IOCTL_MAGIC, 11,
> > > \
> > > + struct f2fs_gc_range)
> > [...]
> > > +
> > > +struct f2fs_gc_range {
> > > + __u32 sync;
> > > + __u64 start;
> > > + __u64 len;
> > > +};
> > [...]
> > > +struct f2fs_move_range {
> > > + __u32 dst_fd; /* destination fd */
> > > + __u64 pos_in; /* start position in src_fd */
> > > + __u64 pos_out; /* start position in dst_fd */
> > > + __u64 len; /* size to move */
> > > +};
> >
> > These two structs are weird because there is implicit padding between the
> > __u32
> > field and the following __u64 field on some 32-bit architectures (e.g.
> > x86_32)
> > but not others (e.g. arm32).
> >
> > But f2fs_compat_ioctl() doesn't handle these two ioctls specially, but
> > rather
> > just calls through to f2fs_ioctl(). That's wrong, and it means that
> > F2FS_IOC_MOVE_RANGE and F2FS_IOC_GARBAGE_COLLECT_RANGE won't work when
> > called
> > from an x86_32 binary on an x86_64 kernel.
>
> Nice catch!
>
> >
> > So something needs to be fixed. I wonder if it's safe to just explicitly
> > add
> > the padding field after the fact. If no one is actually using these two
> > ioctls
> > in a case where both userspace and the kernel lack the implicit padding
> > (e.g.,
> > x86_32 userspace with x86_32 kernel), it should be fine...
>
> IIRC, Jaegeuk added those interfaces, I hope it's not the requirement from
> other
> f2fs userspace developers...if it is, there may be users.
>
> I found one patch in ext4 which fixes the similar issue, I guess we can fix
> this
> with the same way, thoughts?
Agreed. Please fix along with f2fs-tools/f2fs_io.
>
> commit 4d92dc0f00a775dc2e1267b0e00befb783902fe7
> Author: Ben Hutchings <b...@decadent.org.uk>
> Date: Mon May 17 06:00:00 2010 -0400
>
> ext4: Fix compat EXT4_IOC_ADD_GROUP
>
> struct ext4_new_group_input needs to be converted because u64 has
> only 32-bit alignment on some 32-bit architectures, notably i386.
>
> Thanks,
>
> >
> > - Eric
> > .
> >
