Fix: Call zfs_get_name with invalid parameter

[GeLiXin]

Dear all:
zfs_get_name() expect parameter of type zfs_handle_t *zhp , but get an invalid parameter type of zfs_handle_t **zhp actually in libzfs_dataset_cmp(), which may trigger a coredump if called.

libzfs_dataset_cmp() working normally so far, just because all the callers only give datasets whoes type is ZFS_TYPE_FILESYSTEM to it now, we compared their mountpoint and return, luckily.

It's a risk when the caller give snapshot or volume as input parameter.

Signed-off-by: GeLiXin ge.lixin@zte.com.cn

[behlendorf]

LGTM. Nice find, @dweeezil can you take a look at this too.

[dweeezil]

At first glance, this appears to be completely correct but I'm mobile now so I'll look at it again tomorrow.

[dweeezil]

Yes, this fix is of course completely correct and should be pulled into other OpenZFS implementations as well.

On a somewhat related notes, there's a bit of unnecessary void pointer munging related to the cb_handles array. There's no good reason that proper typecasts couldn't be used, for example, in libzfs_add_handle() but, of course, the fix would be mostly cosmetic.

[GeLiXin]

@dweeezil Thanks for your review. I agree with you on that the void pointer munging related to the cb_handles array which can't be used direct is unnecessary. On the other hand, I guess this typecasts is on purpose of making the code easy to be understood, so I just leave it stay the same in this commit.

If you think this typecasts really need to be improved, I can make a further fix.

[behlendorf]

Merged, this is one which should be pushed upstream. We can address the typecasts in a follow up patch if we choose too.

88c4c7a Fix call zfs_get_name() with invalid parameter