[PATCH] usb: dwc3: gadget: Free gadget structure only after freeing endpoints

[PATCH] usb: dwc3: gadget: Free gadget structure only after freeing endpoints

[Jack Pham]

As part of commit e81a7018d93a ("usb: dwc3: allocate gadget structure
dynamically") the dwc3_gadget_release() was added which will free
the dwc->gadget structure upon the device's removal when
usb_del_gadget_udc() is called in dwc3_gadget_exit().

However, simply freeing the gadget results a dangling pointer
situation: the endpoints created in dwc3_gadget_init_endpoints()
have their dep->endpoint.ep_list members chained off the list_head
anchored at dwc->gadget->ep_list.  Thus when dwc->gadget is freed,
the first dwc3_ep in the list now has a dangling prev pointer and
likewise for the next pointer of the dwc3_ep at the tail of the list.
The dwc3_gadget_free_endpoints() that follows will result in a
use-after-free when it calls list_del().

This was caught by enabling KASAN and performing a driver unbind.
The recent commit 568262bf5492 ("usb: dwc3: core: Add shutdown
callback for dwc3") also exposes this as a panic during shutdown.

There are a few possibilities to fix this.  One could be to perform
a list_del() of the gadget->ep_list itself which removes it from
the rest of the dwc3_ep chain.

Another approach is what this patch does, by splitting up the
usb_del_gadget_udc() call into its separate "del" and "put"
components.  This allows dwc3_gadget_free_endpoints() to be
called before the gadget is finally freed with usb_put_gadget().

Fixes: e81a7018d93a ("usb: dwc3: allocate gadget structure dynamically")
Signed-off-by: Jack Pham <jackp@codeaurora.org>
---
 drivers/usb/dwc3/gadget.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 6eab78f8a1a7..c7e5f5a07f3b 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -4062,8 +4062,9 @@ int dwc3_gadget_init(struct dwc3 *dwc)
 
 void dwc3_gadget_exit(struct dwc3 *dwc)
 {
-	usb_del_gadget_udc(dwc->gadget);
+	usb_del_gadget(dwc->gadget);
 	dwc3_gadget_free_endpoints(dwc);
+	usb_del_gadget_put(dwc->gadget);
 	dma_free_coherent(dwc->sysdev, DWC3_BOUNCE_SIZE, dwc->bounce,
 			  dwc->bounce_addr);
 	kfree(dwc->setup_buf);
-- 
2.24.0

[PATCH v2] usb: dwc3: gadget: Free gadget structure only after freeing endpoints

[Jack Pham]

As part of commit e81a7018d93a ("usb: dwc3: allocate gadget structure
dynamically") the dwc3_gadget_release() was added which will free
the dwc->gadget structure upon the device's removal when
usb_del_gadget_udc() is called in dwc3_gadget_exit().

However, simply freeing the gadget results a dangling pointer
situation: the endpoints created in dwc3_gadget_init_endpoints()
have their dep->endpoint.ep_list members chained off the list_head
anchored at dwc->gadget->ep_list.  Thus when dwc->gadget is freed,
the first dwc3_ep in the list now has a dangling prev pointer and
likewise for the next pointer of the dwc3_ep at the tail of the list.
The dwc3_gadget_free_endpoints() that follows will result in a
use-after-free when it calls list_del().

This was caught by enabling KASAN and performing a driver unbind.
The recent commit 568262bf5492 ("usb: dwc3: core: Add shutdown
callback for dwc3") also exposes this as a panic during shutdown.

There are a few possibilities to fix this.  One could be to perform
a list_del() of the gadget->ep_list itself which removes it from
the rest of the dwc3_ep chain.

Another approach is what this patch does, by splitting up the
usb_del_gadget_udc() call into its separate "del" and "put"
components.  This allows dwc3_gadget_free_endpoints() to be
called before the gadget is finally freed with usb_put_gadget().

Fixes: e81a7018d93a ("usb: dwc3: allocate gadget structure dynamically")
Signed-off-by: Jack Pham <jackp@codeaurora.org>
---
v2: Fix silly typo: usb_del_gadget_put -> usb_put_gadget (brain fart
when manually recomposing the patch)

 drivers/usb/dwc3/gadget.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 6eab78f8a1a7..c7e5f5a07f3b 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -4062,8 +4062,9 @@ int dwc3_gadget_init(struct dwc3 *dwc)
 
 void dwc3_gadget_exit(struct dwc3 *dwc)
 {
-	usb_del_gadget_udc(dwc->gadget);
+	usb_del_gadget(dwc->gadget);
 	dwc3_gadget_free_endpoints(dwc);
+	usb_put_gadget(dwc->gadget);
 	dma_free_coherent(dwc->sysdev, DWC3_BOUNCE_SIZE, dwc->bounce,
 			  dwc->bounce_addr);
 	kfree(dwc->setup_buf);
-- 
2.24.0

Re: [PATCH v2] usb: dwc3: gadget: Free gadget structure only after freeing endpoints

[Jack Pham]

Hi Felipe,

I know it may still be early in the merge window but do you have any
feedback for this? We have some internal testers getting hit by this
use-after-free when enabling SLUB_DEBUG or KASAN enabled builds. This
fix resolves the issue in those cases so was hoping for a review soon
so we can eventually queue it up for stable too.

(I sent V2 quickly after V1 but before the kernel bot caught my obvious
blunder on V1.  But I sent V2 as a threaded-reply, so not sure if that
made this get buried in people's inboxes...)

Thanks
Jack

On Sat, May 01, 2021 at 02:35:58AM -0700, Jack Pham wrote:
> As part of commit e81a7018d93a ("usb: dwc3: allocate gadget structure
> dynamically") the dwc3_gadget_release() was added which will free
> the dwc->gadget structure upon the device's removal when
> usb_del_gadget_udc() is called in dwc3_gadget_exit().
> 
> However, simply freeing the gadget results a dangling pointer
> situation: the endpoints created in dwc3_gadget_init_endpoints()
> have their dep->endpoint.ep_list members chained off the list_head
> anchored at dwc->gadget->ep_list.  Thus when dwc->gadget is freed,
> the first dwc3_ep in the list now has a dangling prev pointer and
> likewise for the next pointer of the dwc3_ep at the tail of the list.
> The dwc3_gadget_free_endpoints() that follows will result in a
> use-after-free when it calls list_del().
> 
> This was caught by enabling KASAN and performing a driver unbind.
> The recent commit 568262bf5492 ("usb: dwc3: core: Add shutdown
> callback for dwc3") also exposes this as a panic during shutdown.
> 
> There are a few possibilities to fix this.  One could be to perform
> a list_del() of the gadget->ep_list itself which removes it from
> the rest of the dwc3_ep chain.
> 
> Another approach is what this patch does, by splitting up the
> usb_del_gadget_udc() call into its separate "del" and "put"
> components.  This allows dwc3_gadget_free_endpoints() to be
> called before the gadget is finally freed with usb_put_gadget().
> 
> Fixes: e81a7018d93a ("usb: dwc3: allocate gadget structure dynamically")
> Signed-off-by: Jack Pham <jackp@codeaurora.org>
> ---
> v2: Fix silly typo: usb_del_gadget_put -> usb_put_gadget (brain fart
> when manually recomposing the patch)
> 
>  drivers/usb/dwc3/gadget.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 6eab78f8a1a7..c7e5f5a07f3b 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -4062,8 +4062,9 @@ int dwc3_gadget_init(struct dwc3 *dwc)
>  
>  void dwc3_gadget_exit(struct dwc3 *dwc)
>  {
> -	usb_del_gadget_udc(dwc->gadget);
> +	usb_del_gadget(dwc->gadget);
>  	dwc3_gadget_free_endpoints(dwc);
> +	usb_put_gadget(dwc->gadget);
>  	dma_free_coherent(dwc->sysdev, DWC3_BOUNCE_SIZE, dwc->bounce,
>  			  dwc->bounce_addr);
>  	kfree(dwc->setup_buf);
> -- 
> 2.24.0
> 

-- 
The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH v2] usb: dwc3: gadget: Free gadget structure only after freeing endpoints

[Peter Chen]

On 21-05-01 02:35:58, Jack Pham wrote:
> As part of commit e81a7018d93a ("usb: dwc3: allocate gadget structure
> dynamically") the dwc3_gadget_release() was added which will free
> the dwc->gadget structure upon the device's removal when
> usb_del_gadget_udc() is called in dwc3_gadget_exit().
> 
> However, simply freeing the gadget results a dangling pointer
> situation: the endpoints created in dwc3_gadget_init_endpoints()
> have their dep->endpoint.ep_list members chained off the list_head
> anchored at dwc->gadget->ep_list.  Thus when dwc->gadget is freed,
> the first dwc3_ep in the list now has a dangling prev pointer and
> likewise for the next pointer of the dwc3_ep at the tail of the list.
> The dwc3_gadget_free_endpoints() that follows will result in a
> use-after-free when it calls list_del().
> 
> This was caught by enabling KASAN and performing a driver unbind.
> The recent commit 568262bf5492 ("usb: dwc3: core: Add shutdown
> callback for dwc3") also exposes this as a panic during shutdown.
> 
> There are a few possibilities to fix this.  One could be to perform
> a list_del() of the gadget->ep_list itself which removes it from
> the rest of the dwc3_ep chain.
> 
> Another approach is what this patch does, by splitting up the
> usb_del_gadget_udc() call into its separate "del" and "put"
> components.  This allows dwc3_gadget_free_endpoints() to be
> called before the gadget is finally freed with usb_put_gadget().
> 
> Fixes: e81a7018d93a ("usb: dwc3: allocate gadget structure dynamically")
> Signed-off-by: Jack Pham <jackp@codeaurora.org>
> ---
> v2: Fix silly typo: usb_del_gadget_put -> usb_put_gadget (brain fart
> when manually recomposing the patch)
> 
>  drivers/usb/dwc3/gadget.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 6eab78f8a1a7..c7e5f5a07f3b 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -4062,8 +4062,9 @@ int dwc3_gadget_init(struct dwc3 *dwc)
>  
>  void dwc3_gadget_exit(struct dwc3 *dwc)
>  {
> -	usb_del_gadget_udc(dwc->gadget);
> +	usb_del_gadget(dwc->gadget);
>  	dwc3_gadget_free_endpoints(dwc);
> +	usb_put_gadget(dwc->gadget);
>  	dma_free_coherent(dwc->sysdev, DWC3_BOUNCE_SIZE, dwc->bounce,
>  			  dwc->bounce_addr);
>  	kfree(dwc->setup_buf);
> -- 

Reviewed-by: Peter Chen <peter.chen@kernel.org>

-- 

Thanks,
Peter Chen

Re: [PATCH v2] usb: dwc3: gadget: Free gadget structure only after freeing endpoints

[Felipe Balbi]

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Hi,

Jack Pham <jackp@codeaurora.org> writes:

> As part of commit e81a7018d93a ("usb: dwc3: allocate gadget structure
> dynamically") the dwc3_gadget_release() was added which will free
> the dwc->gadget structure upon the device's removal when
> usb_del_gadget_udc() is called in dwc3_gadget_exit().
>
> However, simply freeing the gadget results a dangling pointer
> situation: the endpoints created in dwc3_gadget_init_endpoints()
> have their dep->endpoint.ep_list members chained off the list_head
> anchored at dwc->gadget->ep_list.  Thus when dwc->gadget is freed,
> the first dwc3_ep in the list now has a dangling prev pointer and
> likewise for the next pointer of the dwc3_ep at the tail of the list.
> The dwc3_gadget_free_endpoints() that follows will result in a
> use-after-free when it calls list_del().
>
> This was caught by enabling KASAN and performing a driver unbind.
> The recent commit 568262bf5492 ("usb: dwc3: core: Add shutdown
> callback for dwc3") also exposes this as a panic during shutdown.
>
> There are a few possibilities to fix this.  One could be to perform
> a list_del() of the gadget->ep_list itself which removes it from
> the rest of the dwc3_ep chain.
>
> Another approach is what this patch does, by splitting up the
> usb_del_gadget_udc() call into its separate "del" and "put"
> components.  This allows dwc3_gadget_free_endpoints() to be
> called before the gadget is finally freed with usb_put_gadget().
>
> Fixes: e81a7018d93a ("usb: dwc3: allocate gadget structure dynamically")
> Signed-off-by: Jack Pham <jackp@codeaurora.org>
> ---
> v2: Fix silly typo: usb_del_gadget_put -> usb_put_gadget (brain fart
> when manually recomposing the patch)

I thought I had acked this one already, looks like I missed it:

Acked-by: Felipe Balbi <balbi@kernel.org>

-- 
balbi

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Re: [PATCH] usb: dwc3: gadget: Free gadget structure only after freeing endpoints

[kernel test robot]

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Hi Jack,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on usb/usb-testing]
[also build test ERROR on peter.chen-usb/for-usb-next linus/master balbi-usb/testing/next v5.12 next-20210430]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Jack-Pham/usb-dwc3-gadget-Free-gadget-structure-only-after-freeing-endpoints/20210501-173239
base:   https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
config: alpha-allmodconfig (attached as .config)
compiler: alpha-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/5b2764c7c290946657e27890a4265bd11bccc0dc
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Jack-Pham/usb-dwc3-gadget-Free-gadget-structure-only-after-freeing-endpoints/20210501-173239
        git checkout 5b2764c7c290946657e27890a4265bd11bccc0dc
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross W=1 ARCH=alpha 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   drivers/usb/dwc3/gadget.c: In function 'dwc3_gadget_exit':
>> drivers/usb/dwc3/gadget.c:4063:2: error: implicit declaration of function 'usb_del_gadget_put'; did you mean 'usb_del_gadget_udc'? [-Werror=implicit-function-declaration]
    4063 |  usb_del_gadget_put(dwc->gadget);
         |  ^~~~~~~~~~~~~~~~~~
         |  usb_del_gadget_udc
   cc1: some warnings being treated as errors


vim +4063 drivers/usb/dwc3/gadget.c

  4058	
  4059	void dwc3_gadget_exit(struct dwc3 *dwc)
  4060	{
  4061		usb_del_gadget(dwc->gadget);
  4062		dwc3_gadget_free_endpoints(dwc);
> 4063		usb_del_gadget_put(dwc->gadget);
  4064		dma_free_coherent(dwc->sysdev, DWC3_BOUNCE_SIZE, dwc->bounce,
  4065				  dwc->bounce_addr);
  4066		kfree(dwc->setup_buf);
  4067		dma_free_coherent(dwc->sysdev, sizeof(*dwc->ep0_trb) * 2,
  4068				  dwc->ep0_trb, dwc->ep0_trb_addr);
  4069	}
  4070	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

[-- Attachment #2: .config.gz --]
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Re: [PATCH] usb: dwc3: gadget: Free gadget structure only after freeing endpoints

[kernel test robot]

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Hi Jack,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on usb/usb-testing]
[also build test ERROR on peter.chen-usb/for-usb-next linus/master balbi-usb/testing/next v5.12 next-20210430]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Jack-Pham/usb-dwc3-gadget-Free-gadget-structure-only-after-freeing-endpoints/20210501-173239
base:   https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
config: x86_64-randconfig-a012-20210501 (attached as .config)
compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 8f5a2a5836cc8e4c1def2bdeb022e7b496623439)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install x86_64 cross compiling tool for clang build
        # apt-get install binutils-x86-64-linux-gnu
        # https://github.com/0day-ci/linux/commit/5b2764c7c290946657e27890a4265bd11bccc0dc
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Jack-Pham/usb-dwc3-gadget-Free-gadget-structure-only-after-freeing-endpoints/20210501-173239
        git checkout 5b2764c7c290946657e27890a4265bd11bccc0dc
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

>> drivers/usb/dwc3/gadget.c:4063:2: error: implicit declaration of function 'usb_del_gadget_put' [-Werror,-Wimplicit-function-declaration]
           usb_del_gadget_put(dwc->gadget);
           ^
   drivers/usb/dwc3/gadget.c:4063:2: note: did you mean 'usb_del_gadget_udc'?
   include/linux/usb/gadget.h:477:13: note: 'usb_del_gadget_udc' declared here
   extern void usb_del_gadget_udc(struct usb_gadget *gadget);
               ^
   1 error generated.


vim +/usb_del_gadget_put +4063 drivers/usb/dwc3/gadget.c

  4058	
  4059	void dwc3_gadget_exit(struct dwc3 *dwc)
  4060	{
  4061		usb_del_gadget(dwc->gadget);
  4062		dwc3_gadget_free_endpoints(dwc);
> 4063		usb_del_gadget_put(dwc->gadget);
  4064		dma_free_coherent(dwc->sysdev, DWC3_BOUNCE_SIZE, dwc->bounce,
  4065				  dwc->bounce_addr);
  4066		kfree(dwc->setup_buf);
  4067		dma_free_coherent(dwc->sysdev, sizeof(*dwc->ep0_trb) * 2,
  4068				  dwc->ep0_trb, dwc->ep0_trb_addr);
  4069	}
  4070	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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