zfs ioctls: use fget_write / fget_read instead of getf wrapper for fget

[avg]

Summary

This allows to ensure that we do not write a file that was opened
for reading only or vice versa.

[delphij]

Looks good to me.

sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c

5438

I think you would want to upstream a change that modifies this to fp = getf(fd); so we don't diverge here.

[avg]

sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c

5438

That makes sense and I would love to do it, but given how hard (for me) is to submit an upstream change it might take me a while.

[avg]

sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c

5423

Please also note that the current code has a bug here: we need CAP_WRITE not CAP_READ.

[smh]

sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c

5438

As matt is on the team here and illumos advocate now is this something he can assist with. I myself has also found that process very time consuming.

[avg]

This change is FreeBSD-specific resolution of https://www.illumos.org/issues/5872

[avg]

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