[PATCH v2] usb: gadget: configfs: Fix use-after-free issue with udc_name

[Macpaul Lin]

On Sat, 2020-07-18 at 10:45 +0800, Macpaul Lin wrote:
> From: Eddie Hung <eddie.hung at mediatek.com>
> 

Well, it's strange, I simply replaced the uploader's name to my
colleague, git send-email pop up this line automatically.

Shouldn't I do that kind of change. It did not happened before.
Do I need to change it back and update patch v3?
 
> There is a use-after-free issue, if access udc_name
> in function gadget_dev_desc_UDC_store after another context
> free udc_name in function unregister_gadget.
> 
> Context 1:
> gadget_dev_desc_UDC_store()->unregister_gadget()->
> free udc_name->set udc_name to NULL
> 
> Context 2:
> gadget_dev_desc_UDC_show()-> access udc_name
> 
> Call trace:
> dump_backtrace+0x0/0x340
> show_stack+0x14/0x1c
> dump_stack+0xe4/0x134
> print_address_description+0x78/0x478
> __kasan_report+0x270/0x2ec
> kasan_report+0x10/0x18
> __asan_report_load1_noabort+0x18/0x20
> string+0xf4/0x138
> vsnprintf+0x428/0x14d0
> sprintf+0xe4/0x12c
> gadget_dev_desc_UDC_show+0x54/0x64
> configfs_read_file+0x210/0x3a0
> __vfs_read+0xf0/0x49c
> vfs_read+0x130/0x2b4
> SyS_read+0x114/0x208
> el0_svc_naked+0x34/0x38
> 
> Add mutex_lock to protect this kind of scenario.
> 
> Signed-off-by: Eddie Hung <eddie.hung at mediatek.com>
> Signed-off-by: Macpaul Lin <macpaul.lin at mediatek.com>
> Reviewed-by: Peter Chen <peter.chen at nxp.com>
> Cc: stable at vger.kernel.org
> ---
> Changes for v2:
>   - Fix typo %s/contex/context, Thanks Peter.
> 
>  drivers/usb/gadget/configfs.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)

Thanks.
Macpaul Lin