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From:   Lu Yao <yaolu@kylinos.cn>
To:     airlied@gmail.com, daniel@ffwll.ch
Cc:     alexander.deucher@amd.com, christian.koenig@amd.com,
        amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org, Lu Yao <yaolu@kylinos.cn>
Subject: [PATCH v2] drm/amdgpu: Fix cat debugfs amdgpu_regs_didt causes kernel null pointer
Date:   Thu, 23 Nov 2023 09:22:34 +0800
Message-Id: <20231123012234.5783-1-yaolu@kylinos.cn>
In-Reply-To: <20231122093509.34302-1-yaolu@kylinos.cn>
References: <20231122093509.34302-1-yaolu@kylinos.cn>
MIME-Version: 1.0
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For 'AMDGPU_FAMILY_SI' family cards, in 'si_common_early_init' func, init
'didt_rreg' and 'didt_wreg' to 'NULL'. But in func
'amdgpu_debugfs_regs_didt_read/write', using 'RREG32_DIDT' 'WREG32_DIDT'
lacks of relevant judgment. And other 'amdgpu_ip_block_version' that use
these two definitions won't be added for 'AMDGPU_FAMILY_SI'.

So, add null pointer judgment before calling.

Signed-off-by: Lu Yao <yaolu@kylinos.cn>
---
Changes in v2:
  1. Drop dev_err message.
  2. Change error code from 'EPERM' to 'EOPNOTSUPP'
Link to v1: https://lore.kernel.org/all/20231122093509.34302-1-yaolu@kylinos.cn/
Thanks Christian for his comments.
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
index a53f436fa9f1..e098cd66fa2a 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
@@ -638,6 +638,9 @@ static ssize_t amdgpu_debugfs_regs_didt_read(struct file *f, char __user *buf,
 	if (size & 0x3 || *pos & 0x3)
 		return -EINVAL;
 
+	if (adev->didt_rreg == NULL)
+		return -EOPNOTSUPP;
+
 	r = pm_runtime_get_sync(adev_to_drm(adev)->dev);
 	if (r < 0) {
 		pm_runtime_put_autosuspend(adev_to_drm(adev)->dev);
@@ -694,6 +697,9 @@ static ssize_t amdgpu_debugfs_regs_didt_write(struct file *f, const char __user
 	if (size & 0x3 || *pos & 0x3)
 		return -EINVAL;
 
+	if (adev->didt_wreg == NULL)
+		return -EOPNOTSUPP;
+
 	r = pm_runtime_get_sync(adev_to_drm(adev)->dev);
 	if (r < 0) {
 		pm_runtime_put_autosuspend(adev_to_drm(adev)->dev);
-- 
2.25.1