Re: KASAN: use-after-free Read in drm_gem_object_release

From: Thomas Zimmermann <tzimmermann@suse.de>
To: butt3rflyh4ck <butterflyhuangxx@gmail.com>, security@kernel.org
Cc: robdclark@chromium.org, airlied@linux.ie,
	syzkaller-bugs@googlegroups.com, dri-devel@lists.freedesktop.org,
	chris@chris-wilson.co.uk, seanpaul@chromium.org,
	sam@ravnborg.org, emil.velikov@collabora.com
Subject: Re: KASAN: use-after-free Read in drm_gem_object_release
Date: Tue, 14 Jul 2020 10:46:16 +0200	[thread overview]
Message-ID: <59a8ed6f-6052-baa3-55a8-9856a2effce9@suse.de> (raw)
In-Reply-To: <4f26b648-1595-3f9a-4236-3d1b3e7134a8@suse.de>

[-- Attachment #1.1.1: Type: text/plain, Size: 7410 bytes --]

Am 14.07.20 um 09:41 schrieb Thomas Zimmermann:
> Hi
> 
> Am 10.07.20 um 10:24 schrieb butt3rflyh4ck:
>> I report a bug (in linux-5.8.0-rc4) found by syzkaller.
>>
>> kernel config: https://github.com/butterflyhack/syzkaller-fuzz/blob/master/v5.8.0-rc4.config
>>
>> I test the reproducer and crash too.
>>
>> In the drm_em_vram_t() function,  ttm_bo_init() function call
>> ttm_bo_init_reserved(),
>> the ttm_bo_init_reserved() function  call ttm_bo_put(), it will free
>> gbo->bo that is struct ttm_buffer_object.
>>
>> then, goto the err_drm_gem_object_release lable,
>> drm_gem_object_release() function will free gbo->bo.base, so cause use
>> after free.
> 
> Thanks for reporting. I think we recently had a patch for this problem,
> [1] but I asked for some changes. Are you in a position to test a fix?
> 
> Best regards
> Thomas
> 
> 
> [1]
> https://lore.kernel.org/dri-devel/20200620062134.82961-1-jiayang5@huawei.com/

I sent out a patchset with this patch and a few additional changes.

https://lore.kernel.org/dri-devel/20200714083238.28479-1-tzimmermann@suse.de/T/#t

Best regards
Thomas

> 
>>
>> crash log:
>> ==================================================================
>> BUG: KASAN: use-after-free in drm_gem_object_release+0xf7/0x120
>> drivers/gpu/drm/drm_gem.c:953
>> Read of size 8 at addr ffff888064dfd928 by task syz-executor.2/1320
>>
>> CPU: 1 PID: 1320 Comm: syz-executor.2 Not tainted 5.8.0-rc4+ #1
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
>> 1.10.2-1ubuntu1 04/01/2014
>> Call Trace:
>>  __dump_stack lib/dump_stack.c:77 [inline]
>>  dump_stack+0x18f/0x20d lib/dump_stack.c:118
>>  print_address_description.constprop.0.cold+0xae/0x436 mm/kasan/report.c:383
>>  __kasan_report mm/kasan/report.c:513 [inline]
>>  kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
>>  drm_gem_object_release+0xf7/0x120 drivers/gpu/drm/drm_gem.c:953
>>  drm_gem_vram_init drivers/gpu/drm/drm_gem_vram_helper.c:211 [inline]
>>  drm_gem_vram_create+0x3e6/0x5e0 drivers/gpu/drm/drm_gem_vram_helper.c:244
>>  drm_gem_vram_fill_create_dumb+0x17a/0x310
>> drivers/gpu/drm/drm_gem_vram_helper.c:615
>>  drm_gem_vram_driver_dumb_create+0x51/0xb0
>> drivers/gpu/drm/drm_gem_vram_helper.c:710
>>  drm_mode_create_dumb+0x27c/0x300 drivers/gpu/drm/drm_dumb_buffers.c:94
>>  drm_ioctl_kernel+0x220/0x2e0 drivers/gpu/drm/drm_ioctl.c:787
>>  drm_ioctl+0x4d2/0x96f drivers/gpu/drm/drm_ioctl.c:887
>>  vfs_ioctl fs/ioctl.c:48 [inline]
>>  ksys_ioctl+0x11a/0x180 fs/ioctl.c:753
>>  __do_sys_ioctl fs/ioctl.c:762 [inline]
>>  __se_sys_ioctl fs/ioctl.c:760 [inline]
>>  __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:760
>>  do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
>>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>> RIP: 0033:0x467a29
>> Code: Bad RIP value.
>> RSP: 002b:00007f98f2d40c48 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
>> RAX: ffffffffffffffda RBX: 000000000076bf00 RCX: 0000000000467a29
>> RDX: 0000000020000040 RSI: 00000000c02064b2 RDI: 0000000000000003
>> RBP: 000000000070c600 R08: 0000000000000000 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f98f2d416bc
>> R13: 0000000000000297 R14: 0000000000702040 R15: 00000000004d2418
>>
>> Allocated by task 1320:
>>  save_stack+0x1b/0x40 mm/kasan/common.c:48
>>  set_track mm/kasan/common.c:56 [inline]
>>  __kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:494
>>  kmem_cache_alloc_trace+0x14f/0x2d0 mm/slab.c:3551
>>  kmalloc include/linux/slab.h:555 [inline]
>>  kzalloc include/linux/slab.h:669 [inline]
>>  drm_gem_vram_create+0x425/0x5e0 drivers/gpu/drm/drm_gem_vram_helper.c:239
>>  drm_gem_vram_fill_create_dumb+0x17a/0x310
>> drivers/gpu/drm/drm_gem_vram_helper.c:615
>>  drm_gem_vram_driver_dumb_create+0x51/0xb0
>> drivers/gpu/drm/drm_gem_vram_helper.c:710
>>  drm_mode_create_dumb+0x27c/0x300 drivers/gpu/drm/drm_dumb_buffers.c:94
>>  drm_ioctl_kernel+0x220/0x2e0 drivers/gpu/drm/drm_ioctl.c:787
>>  drm_ioctl+0x4d2/0x96f drivers/gpu/drm/drm_ioctl.c:887
>>  vfs_ioctl fs/ioctl.c:48 [inline]
>>  ksys_ioctl+0x11a/0x180 fs/ioctl.c:753
>>  __do_sys_ioctl fs/ioctl.c:762 [inline]
>>  __se_sys_ioctl fs/ioctl.c:760 [inline]
>>  __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:760
>>  do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
>>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>>
>> Freed by task 1320:
>>  save_stack+0x1b/0x40 mm/kasan/common.c:48
>>  set_track mm/kasan/common.c:56 [inline]
>>  kasan_set_free_info mm/kasan/common.c:316 [inline]
>>  __kasan_slab_free+0xf5/0x140 mm/kasan/common.c:455
>>  __cache_free mm/slab.c:3426 [inline]
>>  kfree+0x103/0x2c0 mm/slab.c:3757
>>  ttm_bo_release+0xae1/0x1350 drivers/gpu/drm/ttm/ttm_bo.c:632
>>  kref_put include/linux/kref.h:65 [inline]
>>  ttm_bo_put drivers/gpu/drm/ttm/ttm_bo.c:638 [inline]
>>  ttm_bo_init_reserved+0xb04/0xd00 drivers/gpu/drm/ttm/ttm_bo.c:1339
>>  ttm_bo_init+0x10e/0x330 drivers/gpu/drm/ttm/ttm_bo.c:1366
>>  drm_gem_vram_init drivers/gpu/drm/drm_gem_vram_helper.c:202 [inline]
>>  drm_gem_vram_create+0x3c1/0x5e0 drivers/gpu/drm/drm_gem_vram_helper.c:244
>>  drm_gem_vram_fill_create_dumb+0x17a/0x310
>> drivers/gpu/drm/drm_gem_vram_helper.c:615
>>  drm_gem_vram_driver_dumb_create+0x51/0xb0
>> drivers/gpu/drm/drm_gem_vram_helper.c:710
>>  drm_mode_create_dumb+0x27c/0x300 drivers/gpu/drm/drm_dumb_buffers.c:94
>>  drm_ioctl_kernel+0x220/0x2e0 drivers/gpu/drm/drm_ioctl.c:787
>>  drm_ioctl+0x4d2/0x96f drivers/gpu/drm/drm_ioctl.c:887
>>  vfs_ioctl fs/ioctl.c:48 [inline]
>>  ksys_ioctl+0x11a/0x180 fs/ioctl.c:753
>>  __do_sys_ioctl fs/ioctl.c:762 [inline]
>>  __se_sys_ioctl fs/ioctl.c:760 [inline]
>>  __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:760
>>  do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
>>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>>
>> The buggy address belongs to the object at ffff888064dfd800
>>  which belongs to the cache kmalloc-1k of size 1024
>> The buggy address is located 296 bytes inside of
>>  1024-byte region [ffff888064dfd800, ffff888064dfdc00)
>> The buggy address belongs to the page:
>> page:ffffea0001937f40 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0
>> flags: 0xfffe0000000200(slab)
>> raw: 00fffe0000000200 ffffea0000f3c248 ffffea0001ad7388 ffff88806bc00c40
>> raw: 0000000000000000 ffff888064dfd000 0000000100000002 0000000000000000
>> page dumped because: kasan: bad access detected
>>
>> Memory state around the buggy address:
>>  ffff888064dfd800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>  ffff888064dfd880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>> ffff888064dfd900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>                                   ^
>>  ffff888064dfd980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>  ffff888064dfda00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>> ==================================================================
>>
>> Regards,
>>  butt3rflyh4ck.
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

[-- Attachment #1.2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 516 bytes --]

[-- Attachment #2: Type: text/plain, Size: 160 bytes --]

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel