linux-kernel - [PATCH] drm/amd/display/dc/calcs/dce_calcs: Fix a memleak in calculate

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Message-Id: <20220124165552.56106-1-zhou1615@umn.edu>
Date:   Tue, 25 Jan 2022 00:55:51 +0800
From:   Zhou Qingyang <zhou1615@....edu>
To:     zhou1615@....edu
Cc:     kjlu@....edu, Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Lee Jones <lee.jones@...aro.org>,
        Mario Kleiner <mario.kleiner.de@...il.com>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] drm/amd/display/dc/calcs/dce_calcs: Fix a memleak in calculate_bandwidth()

In calculate_bandwidth(), the tag free_sclk and free_yclk are reversed,
which could lead to a memory leak of yclk.

Fix this bug by changing the location of free_sclk and free_yclk.

This bug was found by a static analyzer.

Builds with 'make allyesconfig' show no new warnings,
and our static analyzer no longer warns about this code.

Fixes: 2be8989d0fc2 ("drm/amd/display/dc/calcs/dce_calcs: Move some large variables from the stack to the heap")
Signed-off-by: Zhou Qingyang <zhou1615@....edu>
---
The analysis employs differential checking to identify inconsistent 
security operations (e.g., checks or kfrees) between two code paths 
and confirms that the inconsistent operations are not recovered in the
current function or the callers, so they constitute bugs. 

Note that, as a bug found by static analysis, it can be a false
positive or hard to trigger. Multiple researchers have cross-reviewed
the bug.

 drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c b/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c
index ff5bb152ef49..e6ef36de0825 100644
--- a/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c
+++ b/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c
@@ -2033,10 +2033,10 @@ static void calculate_bandwidth(
 	kfree(surface_type);
 free_tiling_mode:
 	kfree(tiling_mode);
-free_yclk:
-	kfree(yclk);
 free_sclk:
 	kfree(sclk);
+free_yclk:
+	kfree(yclk);
 }
 
 /*******************************************************************************
-- 
2.25.1