linux-kernel - [PATCH 4.4 027/114] drm/amdgpu: Fix a NULL pointer dereference in amdgpu_connector_lcd_native

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20220124183927.960753077@linuxfoundation.org>
Date:   Mon, 24 Jan 2022 19:42:02 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Zhou Qingyang <zhou1615@....edu>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 027/114] drm/amdgpu: Fix a NULL pointer dereference in amdgpu_connector_lcd_native_mode()

From: Zhou Qingyang <zhou1615@....edu>

[ Upstream commit b220110e4cd442156f36e1d9b4914bb9e87b0d00 ]

In amdgpu_connector_lcd_native_mode(), the return value of
drm_mode_duplicate() is assigned to mode, and there is a dereference
of it in amdgpu_connector_lcd_native_mode(), which will lead to a NULL
pointer dereference on failure of drm_mode_duplicate().

Fix this bug add a check of mode.

This bug was found by a static analyzer. 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.

Builds with CONFIG_DRM_AMDGPU=m show no new warnings, and
our static analyzer no longer warns about this code.

Fixes: d38ceaf99ed0 ("drm/amdgpu: add core driver (v4)")
Signed-off-by: Zhou Qingyang <zhou1615@....edu>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
index e1d4115bd6732..80e3b41294e5f 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
@@ -404,6 +404,9 @@ amdgpu_connector_lcd_native_mode(struct drm_encoder *encoder)
 	    native_mode->vdisplay != 0 &&
 	    native_mode->clock != 0) {
 		mode = drm_mode_duplicate(dev, native_mode);
+		if (!mode)
+			return NULL;
+
 		mode->type = DRM_MODE_TYPE_PREFERRED | DRM_MODE_TYPE_DRIVER;
 		drm_mode_set_name(mode);

@@ -418,6 +421,9 @@ amdgpu_connector_lcd_native_mode(struct drm_encoder *encoder)
 		 * simpler.
 		 */
 		mode = drm_cvt_mode(dev, native_mode->hdisplay, native_mode->vdisplay, 60, true, false, false);
+		if (!mode)
+			return NULL;
+
 		mode->type = DRM_MODE_TYPE_PREFERRED | DRM_MODE_TYPE_DRIVER;
 		DRM_DEBUG_KMS("Adding cvt approximation of native panel mode %s\n", mode->name);
 	}
-- 
2.34.1