linux-kernel - [PATCH AUTOSEL 5.5 003/542] drm/dp_mst: fix multiple frees of tx->bytes

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Date:   Fri, 14 Feb 2020 10:39:55 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Colin Ian King <colin.king@...onical.com>,
        Lyude Paul <lyude@...hat.com>, Sasha Levin <sashal@...nel.org>,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 5.5 003/542] drm/dp_mst: fix multiple frees of tx->bytes

From: Colin Ian King <colin.king@...onical.com>

[ Upstream commit 2c8bc91488fc57438c43b3bb19deb7fdbc1e5119 ]

Currently tx->bytes is being freed r->num_transactions number of
times because tx is not being set correctly. Fix this by setting
tx to &r->transactions[i] so that the correct objects are being
freed on each loop iteration.

Addresses-Coverity: ("Double free")
Fixes: 2f015ec6eab6 ("drm/dp_mst: Add sideband down request tracing + selftests")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
Signed-off-by: Lyude Paul <lyude@...hat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191120173509.347490-1-colin.king@canonical.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 141ba31cf5486..cfee59e9c85e5 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -517,8 +517,10 @@ drm_dp_decode_sideband_req(const struct drm_dp_sideband_msg_tx *raw,
 			}
 
 			if (failed) {
-				for (i = 0; i < r->num_transactions; i++)
+				for (i = 0; i < r->num_transactions; i++) {
+					tx = &r->transactions[i];
 					kfree(tx->bytes);
+				}
 				return -ENOMEM;
 			}
 
-- 
2.20.1