diff mbox series

usb: gadget: function: printer: fix use-after-free in __lock_acquire

Message ID 20200605035652.10387-1-qiang.zhang@windriver.com (mailing list archive)
State Superseded
Headers show
Series usb: gadget: function: printer: fix use-after-free in __lock_acquire | expand

Commit Message

Zhang, Qiang June 5, 2020, 3:56 a.m. UTC
From: Zqiang <qiang.zhang@windriver.com>

Fix this by increase object reference count.

BUG: KASAN: use-after-free in __lock_acquire+0x3fd4/0x4180
kernel/locking/lockdep.c:3831
Read of size 8 at addr ffff8880683b0018 by task syz-executor.0/3377

CPU: 1 PID: 3377 Comm: syz-executor.0 Not tainted 5.6.11 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0xce/0x128 lib/dump_stack.c:118
 print_address_description.constprop.4+0x21/0x3c0 mm/kasan/report.c:374
 __kasan_report+0x131/0x1b0 mm/kasan/report.c:506
 kasan_report+0x12/0x20 mm/kasan/common.c:641
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
 __lock_acquire+0x3fd4/0x4180 kernel/locking/lockdep.c:3831
 lock_acquire+0x127/0x350 kernel/locking/lockdep.c:4488
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0x35/0x50 kernel/locking/spinlock.c:159
 printer_ioctl+0x4a/0x110 drivers/usb/gadget/function/f_printer.c:723
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0xfb/0x130 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770
 do_syscall_64+0x9e/0x510 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4531a9
Code: ed 60 fc ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48
89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d
01 f0 ff ff 0f 83 bb 60 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fd14ad72c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000073bfa8 RCX: 00000000004531a9
RDX: fffffffffffffff9 RSI: 000000000000009e RDI: 0000000000000003
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004bbd61
R13: 00000000004d0a98 R14: 00007fd14ad736d4 R15: 00000000ffffffff

Allocated by task 2393:
 save_stack+0x21/0x90 mm/kasan/common.c:72
 set_track mm/kasan/common.c:80 [inline]
 __kasan_kmalloc.constprop.3+0xa7/0xd0 mm/kasan/common.c:515
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:529
 kmem_cache_alloc_trace+0xfa/0x2d0 mm/slub.c:2813
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:669 [inline]
 gprinter_alloc+0xa1/0x870 drivers/usb/gadget/function/f_printer.c:1416
 usb_get_function+0x58/0xc0 drivers/usb/gadget/functions.c:61
 config_usb_cfg_link+0x1ed/0x3e0 drivers/usb/gadget/configfs.c:444
 configfs_symlink+0x527/0x11d0 fs/configfs/symlink.c:202
 vfs_symlink+0x33d/0x5b0 fs/namei.c:4201
 do_symlinkat+0x11b/0x1d0 fs/namei.c:4228
 __do_sys_symlinkat fs/namei.c:4242 [inline]
 __se_sys_symlinkat fs/namei.c:4239 [inline]
 __x64_sys_symlinkat+0x73/0xb0 fs/namei.c:4239
 do_syscall_64+0x9e/0x510 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 3368:
 save_stack+0x21/0x90 mm/kasan/common.c:72
 set_track mm/kasan/common.c:80 [inline]
 kasan_set_free_info mm/kasan/common.c:337 [inline]
 __kasan_slab_free+0x135/0x190 mm/kasan/common.c:476
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:485
 slab_free_hook mm/slub.c:1444 [inline]
 slab_free_freelist_hook mm/slub.c:1477 [inline]
 slab_free mm/slub.c:3034 [inline]
 kfree+0xf7/0x410 mm/slub.c:3995
 gprinter_free+0x49/0xd0 drivers/usb/gadget/function/f_printer.c:1353
 usb_put_function+0x38/0x50 drivers/usb/gadget/functions.c:87
 config_usb_cfg_unlink+0x2db/0x3b0 drivers/usb/gadget/configfs.c:485
 configfs_unlink+0x3b9/0x7f0 fs/configfs/symlink.c:250
 vfs_unlink+0x287/0x570 fs/namei.c:4073
 do_unlinkat+0x4f9/0x620 fs/namei.c:4137
 __do_sys_unlink fs/namei.c:4184 [inline]
 __se_sys_unlink fs/namei.c:4182 [inline]
 __x64_sys_unlink+0x42/0x50 fs/namei.c:4182
 do_syscall_64+0x9e/0x510 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880683b0000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 24 bytes inside of
 1024-byte region [ffff8880683b0000, ffff8880683b0400)
The buggy address belongs to the page:
page:ffffea0001a0ec00 refcount:1 mapcount:0 mapping:ffff88806c00e300
index:0xffff8880683b1800 compound_mapcount: 0
flags: 0x100000000010200(slab|head)
raw: 0100000000010200 0000000000000000 0000000600000001 ffff88806c00e300
raw: ffff8880683b1800 000000008010000a 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Reported-by: Kyungtae Kim <kt0755@gmail.com>
Signed-off-by: Zqiang <qiang.zhang@windriver.com>
---
 drivers/usb/gadget/function/f_printer.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

Comments

Greg KH June 18, 2020, 8:30 a.m. UTC | #1
On Fri, Jun 05, 2020 at 11:56:52AM +0800, qiang.zhang@windriver.com wrote:
> From: Zqiang <qiang.zhang@windriver.com>
> 
> Fix this by increase object reference count.
> 
> BUG: KASAN: use-after-free in __lock_acquire+0x3fd4/0x4180
> kernel/locking/lockdep.c:3831
> Read of size 8 at addr ffff8880683b0018 by task syz-executor.0/3377
> 
> CPU: 1 PID: 3377 Comm: syz-executor.0 Not tainted 5.6.11 #1
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0xce/0x128 lib/dump_stack.c:118
>  print_address_description.constprop.4+0x21/0x3c0 mm/kasan/report.c:374
>  __kasan_report+0x131/0x1b0 mm/kasan/report.c:506
>  kasan_report+0x12/0x20 mm/kasan/common.c:641
>  __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
>  __lock_acquire+0x3fd4/0x4180 kernel/locking/lockdep.c:3831
>  lock_acquire+0x127/0x350 kernel/locking/lockdep.c:4488
>  __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>  _raw_spin_lock_irqsave+0x35/0x50 kernel/locking/spinlock.c:159
>  printer_ioctl+0x4a/0x110 drivers/usb/gadget/function/f_printer.c:723
>  vfs_ioctl fs/ioctl.c:47 [inline]
>  ksys_ioctl+0xfb/0x130 fs/ioctl.c:763
>  __do_sys_ioctl fs/ioctl.c:772 [inline]
>  __se_sys_ioctl fs/ioctl.c:770 [inline]
>  __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770
>  do_syscall_64+0x9e/0x510 arch/x86/entry/common.c:294
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x4531a9
> Code: ed 60 fc ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48
> 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d
> 01 f0 ff ff 0f 83 bb 60 fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007fd14ad72c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 000000000073bfa8 RCX: 00000000004531a9
> RDX: fffffffffffffff9 RSI: 000000000000009e RDI: 0000000000000003
> RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004bbd61
> R13: 00000000004d0a98 R14: 00007fd14ad736d4 R15: 00000000ffffffff
> 
> Allocated by task 2393:
>  save_stack+0x21/0x90 mm/kasan/common.c:72
>  set_track mm/kasan/common.c:80 [inline]
>  __kasan_kmalloc.constprop.3+0xa7/0xd0 mm/kasan/common.c:515
>  kasan_kmalloc+0x9/0x10 mm/kasan/common.c:529
>  kmem_cache_alloc_trace+0xfa/0x2d0 mm/slub.c:2813
>  kmalloc include/linux/slab.h:555 [inline]
>  kzalloc include/linux/slab.h:669 [inline]
>  gprinter_alloc+0xa1/0x870 drivers/usb/gadget/function/f_printer.c:1416
>  usb_get_function+0x58/0xc0 drivers/usb/gadget/functions.c:61
>  config_usb_cfg_link+0x1ed/0x3e0 drivers/usb/gadget/configfs.c:444
>  configfs_symlink+0x527/0x11d0 fs/configfs/symlink.c:202
>  vfs_symlink+0x33d/0x5b0 fs/namei.c:4201
>  do_symlinkat+0x11b/0x1d0 fs/namei.c:4228
>  __do_sys_symlinkat fs/namei.c:4242 [inline]
>  __se_sys_symlinkat fs/namei.c:4239 [inline]
>  __x64_sys_symlinkat+0x73/0xb0 fs/namei.c:4239
>  do_syscall_64+0x9e/0x510 arch/x86/entry/common.c:294
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> Freed by task 3368:
>  save_stack+0x21/0x90 mm/kasan/common.c:72
>  set_track mm/kasan/common.c:80 [inline]
>  kasan_set_free_info mm/kasan/common.c:337 [inline]
>  __kasan_slab_free+0x135/0x190 mm/kasan/common.c:476
>  kasan_slab_free+0xe/0x10 mm/kasan/common.c:485
>  slab_free_hook mm/slub.c:1444 [inline]
>  slab_free_freelist_hook mm/slub.c:1477 [inline]
>  slab_free mm/slub.c:3034 [inline]
>  kfree+0xf7/0x410 mm/slub.c:3995
>  gprinter_free+0x49/0xd0 drivers/usb/gadget/function/f_printer.c:1353
>  usb_put_function+0x38/0x50 drivers/usb/gadget/functions.c:87
>  config_usb_cfg_unlink+0x2db/0x3b0 drivers/usb/gadget/configfs.c:485
>  configfs_unlink+0x3b9/0x7f0 fs/configfs/symlink.c:250
>  vfs_unlink+0x287/0x570 fs/namei.c:4073
>  do_unlinkat+0x4f9/0x620 fs/namei.c:4137
>  __do_sys_unlink fs/namei.c:4184 [inline]
>  __se_sys_unlink fs/namei.c:4182 [inline]
>  __x64_sys_unlink+0x42/0x50 fs/namei.c:4182
>  do_syscall_64+0x9e/0x510 arch/x86/entry/common.c:294
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> The buggy address belongs to the object at ffff8880683b0000
>  which belongs to the cache kmalloc-1k of size 1024
> The buggy address is located 24 bytes inside of
>  1024-byte region [ffff8880683b0000, ffff8880683b0400)
> The buggy address belongs to the page:
> page:ffffea0001a0ec00 refcount:1 mapcount:0 mapping:ffff88806c00e300
> index:0xffff8880683b1800 compound_mapcount: 0
> flags: 0x100000000010200(slab|head)
> raw: 0100000000010200 0000000000000000 0000000600000001 ffff88806c00e300
> raw: ffff8880683b1800 000000008010000a 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Reported-by: Kyungtae Kim <kt0755@gmail.com>
> Signed-off-by: Zqiang <qiang.zhang@windriver.com>
> ---
>  drivers/usb/gadget/function/f_printer.c | 16 ++++++++++++++--
>  1 file changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c
> index 9c7ed2539ff7..8ed1295d7e35 100644
> --- a/drivers/usb/gadget/function/f_printer.c
> +++ b/drivers/usb/gadget/function/f_printer.c
> @@ -31,6 +31,7 @@
>  #include <linux/types.h>
>  #include <linux/ctype.h>
>  #include <linux/cdev.h>
> +#include <linux/kref.h>
>  
>  #include <asm/byteorder.h>
>  #include <linux/io.h>
> @@ -64,7 +65,7 @@ struct printer_dev {
>  	struct usb_gadget	*gadget;
>  	s8			interface;
>  	struct usb_ep		*in_ep, *out_ep;
> -
> +	struct kref             kref;
>  	struct list_head	rx_reqs;	/* List of free RX structs */
>  	struct list_head	rx_reqs_active;	/* List of Active RX xfers */
>  	struct list_head	rx_buffers;	/* List of completed xfers */

Isn't there already a reference count for this structure?  Why not use
that instead?

If not, should this be done to all gadget drivers?  What makes this one
unique?

thanks,

greg k-h
Zhang, Qiang June 22, 2020, 8:47 a.m. UTC | #2
I cannot find a reference count for this structure(printer_dev).
In this scenario:
When the Character device is still open, if you operate the device 
through configfs and execute commands like unlink, the resources 
allocated when the device is bound will be released(printer_dev). After 
that, if you perform ioctl operation again, it will appear 
use-after-free. add kref to show that this resource(printer_dev) will 
also use,
until this character device is close.

Similar problems can occur in f_hid.c.

As for the other gadget drivers, I haven't seen their logical 
implementation,so I'm not sure

thanks,
Zqiang

On 6/18/20 4:30 PM, Greg KH wrote:
> On Fri, Jun 05, 2020 at 11:56:52AM +0800, qiang.zhang@windriver.com wrote:
>> From: Zqiang <qiang.zhang@windriver.com>
>>
>> Fix this by increase object reference count.
>>
>> BUG: KASAN: use-after-free in __lock_acquire+0x3fd4/0x4180
>> kernel/locking/lockdep.c:3831
>> Read of size 8 at addr ffff8880683b0018 by task syz-executor.0/3377
>>
>> CPU: 1 PID: 3377 Comm: syz-executor.0 Not tainted 5.6.11 #1
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>> Call Trace:
>>   __dump_stack lib/dump_stack.c:77 [inline]
>>   dump_stack+0xce/0x128 lib/dump_stack.c:118
>>   print_address_description.constprop.4+0x21/0x3c0 mm/kasan/report.c:374
>>   __kasan_report+0x131/0x1b0 mm/kasan/report.c:506
>>   kasan_report+0x12/0x20 mm/kasan/common.c:641
>>   __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
>>   __lock_acquire+0x3fd4/0x4180 kernel/locking/lockdep.c:3831
>>   lock_acquire+0x127/0x350 kernel/locking/lockdep.c:4488
>>   __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>>   _raw_spin_lock_irqsave+0x35/0x50 kernel/locking/spinlock.c:159
>>   printer_ioctl+0x4a/0x110 drivers/usb/gadget/function/f_printer.c:723
>>   vfs_ioctl fs/ioctl.c:47 [inline]
>>   ksys_ioctl+0xfb/0x130 fs/ioctl.c:763
>>   __do_sys_ioctl fs/ioctl.c:772 [inline]
>>   __se_sys_ioctl fs/ioctl.c:770 [inline]
>>   __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770
>>   do_syscall_64+0x9e/0x510 arch/x86/entry/common.c:294
>>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>> RIP: 0033:0x4531a9
>> Code: ed 60 fc ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48
>> 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d
>> 01 f0 ff ff 0f 83 bb 60 fc ff c3 66 2e 0f 1f 84 00 00 00 00
>> RSP: 002b:00007fd14ad72c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
>> RAX: ffffffffffffffda RBX: 000000000073bfa8 RCX: 00000000004531a9
>> RDX: fffffffffffffff9 RSI: 000000000000009e RDI: 0000000000000003
>> RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004bbd61
>> R13: 00000000004d0a98 R14: 00007fd14ad736d4 R15: 00000000ffffffff
>>
>> Allocated by task 2393:
>>   save_stack+0x21/0x90 mm/kasan/common.c:72
>>   set_track mm/kasan/common.c:80 [inline]
>>   __kasan_kmalloc.constprop.3+0xa7/0xd0 mm/kasan/common.c:515
>>   kasan_kmalloc+0x9/0x10 mm/kasan/common.c:529
>>   kmem_cache_alloc_trace+0xfa/0x2d0 mm/slub.c:2813
>>   kmalloc include/linux/slab.h:555 [inline]
>>   kzalloc include/linux/slab.h:669 [inline]
>>   gprinter_alloc+0xa1/0x870 drivers/usb/gadget/function/f_printer.c:1416
>>   usb_get_function+0x58/0xc0 drivers/usb/gadget/functions.c:61
>>   config_usb_cfg_link+0x1ed/0x3e0 drivers/usb/gadget/configfs.c:444
>>   configfs_symlink+0x527/0x11d0 fs/configfs/symlink.c:202
>>   vfs_symlink+0x33d/0x5b0 fs/namei.c:4201
>>   do_symlinkat+0x11b/0x1d0 fs/namei.c:4228
>>   __do_sys_symlinkat fs/namei.c:4242 [inline]
>>   __se_sys_symlinkat fs/namei.c:4239 [inline]
>>   __x64_sys_symlinkat+0x73/0xb0 fs/namei.c:4239
>>   do_syscall_64+0x9e/0x510 arch/x86/entry/common.c:294
>>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>>
>> Freed by task 3368:
>>   save_stack+0x21/0x90 mm/kasan/common.c:72
>>   set_track mm/kasan/common.c:80 [inline]
>>   kasan_set_free_info mm/kasan/common.c:337 [inline]
>>   __kasan_slab_free+0x135/0x190 mm/kasan/common.c:476
>>   kasan_slab_free+0xe/0x10 mm/kasan/common.c:485
>>   slab_free_hook mm/slub.c:1444 [inline]
>>   slab_free_freelist_hook mm/slub.c:1477 [inline]
>>   slab_free mm/slub.c:3034 [inline]
>>   kfree+0xf7/0x410 mm/slub.c:3995
>>   gprinter_free+0x49/0xd0 drivers/usb/gadget/function/f_printer.c:1353
>>   usb_put_function+0x38/0x50 drivers/usb/gadget/functions.c:87
>>   config_usb_cfg_unlink+0x2db/0x3b0 drivers/usb/gadget/configfs.c:485
>>   configfs_unlink+0x3b9/0x7f0 fs/configfs/symlink.c:250
>>   vfs_unlink+0x287/0x570 fs/namei.c:4073
>>   do_unlinkat+0x4f9/0x620 fs/namei.c:4137
>>   __do_sys_unlink fs/namei.c:4184 [inline]
>>   __se_sys_unlink fs/namei.c:4182 [inline]
>>   __x64_sys_unlink+0x42/0x50 fs/namei.c:4182
>>   do_syscall_64+0x9e/0x510 arch/x86/entry/common.c:294
>>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>>
>> The buggy address belongs to the object at ffff8880683b0000
>>   which belongs to the cache kmalloc-1k of size 1024
>> The buggy address is located 24 bytes inside of
>>   1024-byte region [ffff8880683b0000, ffff8880683b0400)
>> The buggy address belongs to the page:
>> page:ffffea0001a0ec00 refcount:1 mapcount:0 mapping:ffff88806c00e300
>> index:0xffff8880683b1800 compound_mapcount: 0
>> flags: 0x100000000010200(slab|head)
>> raw: 0100000000010200 0000000000000000 0000000600000001 ffff88806c00e300
>> raw: ffff8880683b1800 000000008010000a 00000001ffffffff 0000000000000000
>> page dumped because: kasan: bad access detected
>>
>> Reported-by: Kyungtae Kim <kt0755@gmail.com>
>> Signed-off-by: Zqiang <qiang.zhang@windriver.com>
>> ---
>>   drivers/usb/gadget/function/f_printer.c | 16 ++++++++++++++--
>>   1 file changed, 14 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c
>> index 9c7ed2539ff7..8ed1295d7e35 100644
>> --- a/drivers/usb/gadget/function/f_printer.c
>> +++ b/drivers/usb/gadget/function/f_printer.c
>> @@ -31,6 +31,7 @@
>>   #include <linux/types.h>
>>   #include <linux/ctype.h>
>>   #include <linux/cdev.h>
>> +#include <linux/kref.h>
>>   
>>   #include <asm/byteorder.h>
>>   #include <linux/io.h>
>> @@ -64,7 +65,7 @@ struct printer_dev {
>>   	struct usb_gadget	*gadget;
>>   	s8			interface;
>>   	struct usb_ep		*in_ep, *out_ep;
>> -
>> +	struct kref             kref;
>>   	struct list_head	rx_reqs;	/* List of free RX structs */
>>   	struct list_head	rx_reqs_active;	/* List of Active RX xfers */
>>   	struct list_head	rx_buffers;	/* List of completed xfers */
> 
> Isn't there already a reference count for this structure?  Why not use
> that instead?
> 
> If not, should this be done to all gadget drivers?  What makes this one
> unique?
> 
> thanks,
> 
> greg k-h
>
diff mbox series

Patch

diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c
index 9c7ed2539ff7..8ed1295d7e35 100644
--- a/drivers/usb/gadget/function/f_printer.c
+++ b/drivers/usb/gadget/function/f_printer.c
@@ -31,6 +31,7 @@ 
 #include <linux/types.h>
 #include <linux/ctype.h>
 #include <linux/cdev.h>
+#include <linux/kref.h>
 
 #include <asm/byteorder.h>
 #include <linux/io.h>
@@ -64,7 +65,7 @@  struct printer_dev {
 	struct usb_gadget	*gadget;
 	s8			interface;
 	struct usb_ep		*in_ep, *out_ep;
-
+	struct kref             kref;
 	struct list_head	rx_reqs;	/* List of free RX structs */
 	struct list_head	rx_reqs_active;	/* List of Active RX xfers */
 	struct list_head	rx_buffers;	/* List of completed xfers */
@@ -218,6 +219,13 @@  static inline struct usb_endpoint_descriptor *ep_desc(struct usb_gadget *gadget,
 
 /*-------------------------------------------------------------------------*/
 
+static void printer_dev_free(struct kref *kref)
+{
+	struct printer_dev *dev = container_of(kref, struct printer_dev, kref);
+
+	kfree(dev);
+}
+
 static struct usb_request *
 printer_req_alloc(struct usb_ep *ep, unsigned len, gfp_t gfp_flags)
 {
@@ -348,6 +356,7 @@  printer_open(struct inode *inode, struct file *fd)
 
 	spin_unlock_irqrestore(&dev->lock, flags);
 
+	kref_get(&dev->kref);
 	DBG(dev, "printer_open returned %x\n", ret);
 	return ret;
 }
@@ -365,6 +374,7 @@  printer_close(struct inode *inode, struct file *fd)
 	dev->printer_status &= ~PRINTER_SELECTED;
 	spin_unlock_irqrestore(&dev->lock, flags);
 
+	kref_put(&dev->kref, printer_dev_free);
 	DBG(dev, "printer_close\n");
 
 	return 0;
@@ -1350,7 +1360,8 @@  static void gprinter_free(struct usb_function *f)
 	struct f_printer_opts *opts;
 
 	opts = container_of(f->fi, struct f_printer_opts, func_inst);
-	kfree(dev);
+
+	kref_put(&dev->kref, printer_dev_free);
 	mutex_lock(&opts->lock);
 	--opts->refcnt;
 	mutex_unlock(&opts->lock);
@@ -1419,6 +1430,7 @@  static struct usb_function *gprinter_alloc(struct usb_function_instance *fi)
 		return ERR_PTR(-ENOMEM);
 	}
 
+	kref_init(&dev->kref);
 	++opts->refcnt;
 	dev->minor = opts->minor;
 	dev->pnp_string = opts->pnp_string;