net/smc: use after free fix in smc_wr_tx_put_slot()

[ Upstream commit e438bae43c1e08e688c09c410407b59fc1c173b4 ]

In smc_wr_tx_put_slot() field pend->idx is used after being
cleared. That means always idx 0 is cleared in the wr_tx_mask.
This results in a broken administration of available WR send
payload buffers.

Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

net/smc/smc_wr.c

@@ -223,12 +223,14 @@ int smc_wr_tx_put_slot(struct smc_link *link,
 
 	pend = container_of(wr_pend_priv, struct smc_wr_tx_pend, priv);
 	if (pend->idx < link->wr_tx_cnt) {
+		u32 idx = pend->idx;
+
 		/* clear the full struct smc_wr_tx_pend including .priv */
 		memset(&link->wr_tx_pends[pend->idx], 0,
 		       sizeof(link->wr_tx_pends[pend->idx]));
 		memset(&link->wr_tx_bufs[pend->idx], 0,
 		       sizeof(link->wr_tx_bufs[pend->idx]));
-		test_and_clear_bit(pend->idx, link->wr_tx_mask);
+		test_and_clear_bit(idx, link->wr_tx_mask);
 		return 1;
 	}