[PATCH v2] misc: fastrpc: Fix double free of 'buf' in error path

[PATCH v2] misc: fastrpc: Fix double free of 'buf' in error path

[Sukrut Bellary]

smatch warning:
drivers/misc/fastrpc.c:1926 fastrpc_req_mmap() error: double free of 'buf'

In fastrpc_req_mmap() error path, the fastrpc buffer is freed in
fastrpc_req_munmap_impl() if unmap is successful.

But in the end, there is an unconditional call to fastrpc_buf_free().
So the above case triggers the double free of fastrpc buf.

Fixes: 72fa6f7820c4 ("misc: fastrpc: Rework fastrpc_req_munmap")
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Sukrut Bellary <sukrut.bellary@linux.com>
---
This is based on static analysis. Compilation tested.
---
Changes in v2: 
- Fixed the commit message.
- Addressed the review comment about deleting buf from the list
  before freeing.
- Link to v1: https://lore.kernel.org/all/20230518100829.515143-1-sukrut.bellary@linux.com/
---
 drivers/misc/fastrpc.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index f48466960f1b..b3b520fcfb75 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -1882,7 +1882,8 @@ static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
 				      &args[0]);
 	if (err) {
 		dev_err(dev, "mmap error (len 0x%08llx)\n", buf->size);
-		goto err_invoke;
+		fastrpc_buf_free(buf);
+		return err;
 	}
 
 	/* update the buffer to be able to deallocate the memory on the DSP */
@@ -1922,8 +1923,6 @@ static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
 
 err_assign:
 	fastrpc_req_munmap_impl(fl, buf);
-err_invoke:
-	fastrpc_buf_free(buf);
 
 	return err;
 }
-- 
2.34.1

Re: [PATCH v2] misc: fastrpc: Fix double free of 'buf' in error path

[Srinivas Kandagatla]

On 02/06/2023 12:36, Sukrut Bellary wrote:
> smatch warning:
> drivers/misc/fastrpc.c:1926 fastrpc_req_mmap() error: double free of 'buf'
> 
> In fastrpc_req_mmap() error path, the fastrpc buffer is freed in
> fastrpc_req_munmap_impl() if unmap is successful.
> 
> But in the end, there is an unconditional call to fastrpc_buf_free().
> So the above case triggers the double free of fastrpc buf.
> 
> Fixes: 72fa6f7820c4 ("misc: fastrpc: Rework fastrpc_req_munmap")
> Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
> Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>
> Reviewed-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Not sure how was this reviewed-by picked up on this patch.

Suggested-by will be a right choice here.

Will manually edit before applying it.

--srini

> Signed-off-by: Sukrut Bellary <sukrut.bellary@linux.com>
> ---
> This is based on static analysis. Compilation tested.
> ---
> Changes in v2:
> - Fixed the commit message.
> - Addressed the review comment about deleting buf from the list
>    before freeing.
> - Link to v1: https://lore.kernel.org/all/20230518100829.515143-1-sukrut.bellary@linux.com/
> ---
>   drivers/misc/fastrpc.c | 5 ++---
>   1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index f48466960f1b..b3b520fcfb75 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -1882,7 +1882,8 @@ static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
>   				      &args[0]);
>   	if (err) {
>   		dev_err(dev, "mmap error (len 0x%08llx)\n", buf->size);
> -		goto err_invoke;
> +		fastrpc_buf_free(buf);
> +		return err;
>   	}
>   
>   	/* update the buffer to be able to deallocate the memory on the DSP */
> @@ -1922,8 +1923,6 @@ static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
>   
>   err_assign:
>   	fastrpc_req_munmap_impl(fl, buf);
> -err_invoke:
> -	fastrpc_buf_free(buf);
>   
>   	return err;
>   }

Re: [PATCH v2] misc: fastrpc: Fix double free of 'buf' in error path

[Srinivas Kandagatla]

On Fri, 02 Jun 2023 04:36:02 -0700, Sukrut Bellary wrote:
> smatch warning:
> drivers/misc/fastrpc.c:1926 fastrpc_req_mmap() error: double free of 'buf'
> 
> In fastrpc_req_mmap() error path, the fastrpc buffer is freed in
> fastrpc_req_munmap_impl() if unmap is successful.
> 
> But in the end, there is an unconditional call to fastrpc_buf_free().
> So the above case triggers the double free of fastrpc buf.
> 
> [...]

Applied, thanks!

[1/1] misc: fastrpc: Fix double free of 'buf' in error path
      commit: 5b3006fffce89706a12741d7f657869ca2be1640

Best regards,
-- 
Srinivas Kandagatla <srinivas.kandagatla@linaro.org>

Re: [PATCH v2] misc: fastrpc: Fix double free of 'buf' in error path

[Dan Carpenter]

On Mon, Jun 12, 2023 at 11:58:01AM +0100, Srinivas Kandagatla wrote:
> 
> On Fri, 02 Jun 2023 04:36:02 -0700, Sukrut Bellary wrote:
> > smatch warning:
> > drivers/misc/fastrpc.c:1926 fastrpc_req_mmap() error: double free of 'buf'
> > 
> > In fastrpc_req_mmap() error path, the fastrpc buffer is freed in
> > fastrpc_req_munmap_impl() if unmap is successful.
> > 
> > But in the end, there is an unconditional call to fastrpc_buf_free().
> > So the above case triggers the double free of fastrpc buf.
> > 
> > [...]
> 
> Applied, thanks!
> 
> [1/1] misc: fastrpc: Fix double free of 'buf' in error path
>       commit: 5b3006fffce89706a12741d7f657869ca2be1640
> 

This patch wasn't actually applied.  I'm not sure what went wrong.

regards,
dan carpenter

Re: [PATCH v2] misc: fastrpc: Fix double free of 'buf' in error path

[Srinivas Kandagatla]

On 15/08/2024 10:25, Dan Carpenter wrote:
> On Mon, Jun 12, 2023 at 11:58:01AM +0100, Srinivas Kandagatla wrote:
>>
>> On Fri, 02 Jun 2023 04:36:02 -0700, Sukrut Bellary wrote:
>>> smatch warning:
>>> drivers/misc/fastrpc.c:1926 fastrpc_req_mmap() error: double free of 'buf'
>>>
>>> In fastrpc_req_mmap() error path, the fastrpc buffer is freed in
>>> fastrpc_req_munmap_impl() if unmap is successful.
>>>
>>> But in the end, there is an unconditional call to fastrpc_buf_free().
>>> So the above case triggers the double free of fastrpc buf.
>>>
>>> [...]
>>
>> Applied, thanks!
>>
>> [1/1] misc: fastrpc: Fix double free of 'buf' in error path
>>        commit: 5b3006fffce89706a12741d7f657869ca2be1640
>>
> 
> This patch wasn't actually applied.  I'm not sure what went wrong.

Am not sure either, its now applied!

thanks for checking this.

--srini
> 
> regards,
> dan carpenter
> 

Re: [PATCH v2] misc: fastrpc: Fix double free of 'buf' in error path

[Srinivas Kandagatla]

On Fri, 02 Jun 2023 04:36:02 -0700, Sukrut Bellary wrote:
> smatch warning:
> drivers/misc/fastrpc.c:1926 fastrpc_req_mmap() error: double free of 'buf'
> 
> In fastrpc_req_mmap() error path, the fastrpc buffer is freed in
> fastrpc_req_munmap_impl() if unmap is successful.
> 
> But in the end, there is an unconditional call to fastrpc_buf_free().
> So the above case triggers the double free of fastrpc buf.
> 
> [...]

Applied, thanks!

[1/1] misc: fastrpc: Fix double free of 'buf' in error path
      commit: b056e4e23acbbbf12fa011caa781f7cecbd5b311

Best regards,
-- 
Srinivas Kandagatla <srinivas.kandagatla@linaro.org>