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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Ursula Braun <ubraun@linux.ibm.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 081/243] net/smc: use after free fix in smc_wr_tx_put_slot()
Date:   Wed, 11 Dec 2019 16:04:03 +0100
Message-Id: <20191211150344.576230307@linuxfoundation.org>
In-Reply-To: <20191211150339.185439726@linuxfoundation.org>
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From: Ursula Braun <ursula.braun@linux.ibm.com>

[ 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 | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/smc/smc_wr.c b/net/smc/smc_wr.c
index 3c458d2798557..c2694750a6a8a 100644
--- a/net/smc/smc_wr.c
+++ b/net/smc/smc_wr.c
@@ -215,12 +215,14 @@ 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;
 	}
 
-- 
2.20.1