He broke wind whilst doing ghusl from janaabah; is his ghusl invalidated?

Passing wind is one of the things that invalidate wudoo’ but
it is not one of the things that invalidate ghusl. Based on this, if a
person touches his private part, urinates or passes wind whilst doing ghusl,
he should complete his ghusl, then do wudoo’ afterwards. 

The basic principle is that if ghusl is done following major
impurity, then it suffices for wudoo’. If a person is junub (impure
following sexual activity) and he does ghusl, then that suffices for wudoo’,
because Allaah says (interpretation of the meaning): 

“If you are in a state of
Janaaba (i.e. after a sexual discharge), purify yourselves (bathe your whole
body)”

[al-Maa’idah 5:6]

He does not have to do wudoo’ after doing ghusl, but if one
of the things that invalidate wudoo’ takes place whilst doing ghusl or
afterwards, then he has to do wudoo’ for prayer. But if he does not break
his wudoo’ then his ghusl from janaabah suffices for wudoo’, whether he did
wudoo’ before ghusl or not. But it is essential to pay attention to rinsing
the mouth and nose, because these are essential for both wudoo’ and ghusl. 

Majmoo’ Fataawa al-Shaykh Ibn ‘Uthaymeen,
11/228 

And Allaah knows best.