linux-kernel - [PATCH -next] drm/amdgpu: double free error and freeing uninitialized null pointer

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Date:   Sun, 10 Jul 2022 18:59:09 +0530
From:   Sebin Sebastian <mailmesebin00@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Sebin Sebastian <mailmesebin00@...il.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>,
        Nirmoy Das <nirmoy.das@....com>,
        Lijo Lazar <lijo.lazar@....com>,
        Tom St Denis <tom.stdenis@....com>,
        Evan Quan <evan.quan@....com>,
        Somalapuram Amaranath <Amaranath.Somalapuram@....com>,
        André Almeida <andrealmeid@...lia.com>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH -next] drm/amdgpu: double free error and freeing uninitialized null pointer

Fix two coverity warning's double free and and an uninitialized pointer
read. Both tmp and new are pointing at same address and both are freed
which leads to double free. Freeing tmp in the condition after new is
assigned with new address fixes the double free issue. new is not
initialized to null which also leads to a free on an uninitialized
pointer.
Coverity issue: 1518665 (uninitialized pointer read)
		1518679 (double free)

Signed-off-by: Sebin Sebastian <mailmesebin00@...il.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
index f3b3c688e4e7..d82fe0e1b06b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
@@ -1660,7 +1660,7 @@ static ssize_t amdgpu_reset_dump_register_list_write(struct file *f,
 {
 	struct amdgpu_device *adev = (struct amdgpu_device *)file_inode(f)->i_private;
 	char reg_offset[11];
-	uint32_t *new, *tmp = NULL;
+	uint32_t *new = NULL, *tmp = NULL;
 	int ret, i = 0, len = 0;
 
 	do {
@@ -1692,17 +1692,19 @@ static ssize_t amdgpu_reset_dump_register_list_write(struct file *f,
 		goto error_free;
 	}
 	ret = down_write_killable(&adev->reset_domain->sem);
-	if (ret)
+	if (ret) {
+		kfree(tmp);
 		goto error_free;
+	}
 
 	swap(adev->reset_dump_reg_list, tmp);
 	swap(adev->reset_dump_reg_value, new);
 	adev->num_regs = i;
 	up_write(&adev->reset_domain->sem);
+	kfree(tmp);
 	ret = size;
 
 error_free:
-	kfree(tmp);
 	kfree(new);
 	return ret;
 }
-- 
2.34.1