[PATCHv2 -next] drm/amdgpu: double free error and freeing uninitialized null pointer

[PATCHv2 -next] drm/amdgpu: double free error and freeing uninitialized null pointer

[Sebin Sebastian]

Fix a double free and an uninitialized pointer read error. Both tmp and
new are pointing at same address and both are freed which leads to
double free. Adding a check to verify if new and tmp are free in the
error_free label fixes the double free issue. new is not initialized to
null which also leads to a free on an uninitialized pointer.

Suggested by: S. Amaranath <Amaranath.Somalapuram@amd.com>
Signed-off-by: Sebin Sebastian <mailmesebin00@gmail.com>
---
Changes in v2:
Updated patch body as suggested by André Almeida <andrealmeid@igalia.com>
Reworked to implement a check in error_free for fixing double free error
as suggested by S. Amaranath <Amaranath.Somalapuram@amd.com>

 drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
index e2eec985adb3..cb00c7d6f50b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
@@ -1705,7 +1705,7 @@ 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 {
@@ -1747,7 +1747,8 @@ static ssize_t amdgpu_reset_dump_register_list_write(struct file *f,
 	ret = size;
 
 error_free:
-	kfree(tmp);
+	if (tmp != new)
+		kfree(tmp);
 	kfree(new);
 	return ret;
 }
-- 
2.34.1

RE: [PATCHv2 -next] drm/amdgpu: double free error and freeing uninitialized null pointer

[Quan, Evan]

[AMD Official Use Only - General]

Reviewed-by: Evan Quan <evan.quan@amd.com>

> -----Original Message-----
> From: Sebin Sebastian <mailmesebin00@gmail.com>
> Sent: Saturday, July 30, 2022 11:47 AM
> Cc: mailmesebin00@gmail.com; Deucher, Alexander
> <Alexander.Deucher@amd.com>; Koenig, Christian
> <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; David
> Airlie <airlied@linux.ie>; Daniel Vetter <daniel@ffwll.ch>; Nirmoy Das
> <nirmoy.das@amd.com>; Lazar, Lijo <Lijo.Lazar@amd.com>; Quan, Evan
> <Evan.Quan@amd.com>; StDenis, Tom <Tom.StDenis@amd.com>;
> Somalapuram, Amaranath <Amaranath.Somalapuram@amd.com>; André
> Almeida <andrealmeid@igalia.com>; amd-gfx@lists.freedesktop.org; dri-
> devel@lists.freedesktop.org; linux-kernel@vger.kernel.org
> Subject: [PATCHv2 -next] drm/amdgpu: double free error and freeing
> uninitialized null pointer
> 
> Fix a double free and an uninitialized pointer read error. Both tmp and
> new are pointing at same address and both are freed which leads to
> double free. Adding a check to verify if new and tmp are free in the
> error_free label fixes the double free issue. new is not initialized to
> null which also leads to a free on an uninitialized pointer.
> 
> Suggested by: S. Amaranath <Amaranath.Somalapuram@amd.com>
> Signed-off-by: Sebin Sebastian <mailmesebin00@gmail.com>
> ---
> Changes in v2:
> Updated patch body as suggested by André Almeida
> <andrealmeid@igalia.com>
> Reworked to implement a check in error_free for fixing double free error
> as suggested by S. Amaranath <Amaranath.Somalapuram@amd.com>
> 
>  drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> index e2eec985adb3..cb00c7d6f50b 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> @@ -1705,7 +1705,7 @@ 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 {
> @@ -1747,7 +1747,8 @@ static ssize_t
> amdgpu_reset_dump_register_list_write(struct file *f,
>  	ret = size;
> 
>  error_free:
> -	kfree(tmp);
> +	if (tmp != new)
> +		kfree(tmp);
>  	kfree(new);
>  	return ret;
>  }
> --
> 2.34.1

Re: [PATCHv2 -next] drm/amdgpu: double free error and freeing uninitialized null pointer

[André Almeida]

Às 00:46 de 30/07/22, Sebin Sebastian escreveu:
> Fix a double free and an uninitialized pointer read error. Both tmp and
> new are pointing at same address and both are freed which leads to
> double free. Adding a check to verify if new and tmp are free in the
> error_free label fixes the double free issue. new is not initialized to
> null which also leads to a free on an uninitialized pointer.
> 
> Suggested by: S. Amaranath <Amaranath.Somalapuram@amd.com>
> Signed-off-by: Sebin Sebastian <mailmesebin00@gmail.com>

Reviewed-by: André Almeida <andrealmeid@igalia.com>

Re: [PATCHv2 -next] drm/amdgpu: double free error and freeing uninitialized null pointer

[Alex Deucher]

Applied.  Thanks!

Alex

On Mon, Aug 1, 2022 at 1:08 PM André Almeida <andrealmeid@igalia.com> wrote:
>
> Às 00:46 de 30/07/22, Sebin Sebastian escreveu:
> > Fix a double free and an uninitialized pointer read error. Both tmp and
> > new are pointing at same address and both are freed which leads to
> > double free. Adding a check to verify if new and tmp are free in the
> > error_free label fixes the double free issue. new is not initialized to
> > null which also leads to a free on an uninitialized pointer.
> >
> > Suggested by: S. Amaranath <Amaranath.Somalapuram@amd.com>
> > Signed-off-by: Sebin Sebastian <mailmesebin00@gmail.com>
>
> Reviewed-by: André Almeida <andrealmeid@igalia.com>