Three days after becoming the first Australian to hit a century in the first session of a test, Warner blasted a half-century from just 23 balls, with seven fours and three sixes.
The fastest 50 in Test history remains the 21-ball blast by Pakistan captain Misbah-ul-Haq against Australia at Abu Dhabi in 2014.
Warner was dismissed four balls later for 55, bowled by Wahab Riaz as he attempted to hit over mid-wicket.
Pakistan was without bowler Mohammad Amir, who was having scans on a side strain picked up in training earlier in the day.
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Earlier, Josh Hazelwood (4-55) took the remaining two wickets in Pakistan's innings to bowl the tourists out for 315, trailing Australia by 223 runs.
Younis Khan made 175 not out off 334 balls, with 18 fours and three sixes, including a huge six over long-on off Nathan Lyon (3-115) to reach his 150, for the 13th time in his test career.
Smith opted against enforcing the follow-on, giving his bowlers some rest ahead a likely declaration later Friday as Australia pushed for a series clean sweep.
Earlier Friday, Australia team doctor Peter Brukner said opening batsman Renshaw had been ruled out for the remainder of the third test due to concussion after being hit on the helmet twice in three days.