Volume 3, Book 29, Number 67:
Narrated Ibn ‘Abbas (radiallaahu `anhu):
I heard the Prophet (sallallaahu `alayhi wasallam) delivering a sermon at ‘Arafat saying, “If a Muhrim does not find slippers, he could wear Khuffs (but he has to cut short the Khuffs below the ankles), and if he does not find an Izar (a waist sheet for wrapping the lower half of the body) he could wear trousers.”
Volume 3, Book 29, Number 68:
Narrated Abdullah (radiallaahu `anhu):
Allah’s Apostle (sallallaahu `alayhi wasallam) was asked what sort of clothes a Muhrim should wear. He replied, “He should not wear a shirt, turbans, trousers, a hooded cloak, or a dress perfumed with saffron or Wars; and if slippers are not available he can wear Khuffs but he should cut them so that they reach below the ankles.
Volume 3, Book 29, Number 69:
Narrated Ibn Abbas (radiallaahu `anhu):
The Prophet (sallallaahu `alayhi wasallam) delivered a sermon at ‘Arafat and said, “Whoever does not get an Izar can wear trousers, and whoever cannot get a pair of shoes can wear Khuffs.”
It is not permissible for a man who is in ihraam to wear socks, but it is permissible for a woman to do that.
The Standing Committee was asked: what is the ruling on wearing socks on the feet and doing tawaaf al-qudoom in them during Hajj, and doing the tawaaf of ‘Umrah in them during ‘Umrah?
It is not permissible for men to wear socks when in ihraam for Hajj or ‘Umrah. If he needs to wear them because of sickness etc, then he must offer a ransom (fidyah), which is to fast for three days, or to feed six poor persons, giving each one half a saa’ of dates or similar food, or to sacrifice a sheep.
Fataawa al-Lajnah al-Daa’imah li’l-Buhooth al-‘Ilmiyyah wa’l-Ifta’, 11/183.
“Whoever does not find an Izar (chadar) can wear trousers”. I doubt if there’s anyone today who fits this description. Going for Hajj, spending huge sums of money, one just might find enough to buy two plain white sheets for his Ihraam, right?
Dealt with already. See this.