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From:   Christophe JAILLET <christophe.jaillet@wanadoo.fr>
To:     Alex Deucher <alexander.deucher@amd.com>,
        =?UTF-8?q?Christian=20K=C3=B6nig?= <christian.koenig@amd.com>,
        "Pan, Xinhui" <Xinhui.Pan@amd.com>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Lijo Lazar <lijo.lazar@amd.com>,
        Mario Limonciello <mario.limonciello@amd.com>
Cc:     linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org,
        Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
        amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org
Subject: [PATCH] drm/amd: Fix the size of a buffer in amdgpu_vcn_idle_work_handler()
Date:   Fri, 22 Sep 2023 21:27:25 +0200
Message-Id: <d8a9cda0c4c391458ddd63d1be88f2a757f6a5d0.1695410820.git.christophe.jaillet@wanadoo.fr>
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In order to be sure that fw_name is not truncated, this buffer should be
at least 41 bytes long.

Let the compiler compute the correct length by itself.

When building with W=1, this fixes the following warnings:

  drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c: In function ‘amdgpu_vcn_early_init’:
  drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c:95:58: error: ‘snprintf’ output may be truncated before the last format character [-Werror=format-truncation=]
     95 |         snprintf(fw_name, sizeof(fw_name), "amdgpu/%s.bin", ucode_prefix);
        |                                                          ^
  drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c:95:9: note: ‘snprintf’ output between 12 and 41 bytes into a destination of size 40
     95 |         snprintf(fw_name, sizeof(fw_name), "amdgpu/%s.bin", ucode_prefix);
        |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fixes: 69939009bde7 ("drm/amd: Load VCN microcode during early_init")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c
index c93f3a4c0e31..f8cd55a0d1f0 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c
@@ -88,7 +88,7 @@ static void amdgpu_vcn_idle_work_handler(struct work_struct *work);
 int amdgpu_vcn_early_init(struct amdgpu_device *adev)
 {
 	char ucode_prefix[30];
-	char fw_name[40];
+	char fw_name[sizeof(ucode_prefix) + sizeof("amdgpu/.bin") - 1];
 	int r;
 
 	amdgpu_ucode_ip_version_decode(adev, UVD_HWIP, ucode_prefix, sizeof(ucode_prefix));
-- 
2.34.1