KASAN: use-after-free Read in vgem_fence_attach

Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
linux-4.14	KASAN: use-after-free Read in vgem_fence_attach_ioctl	C			1	654d	1514d	0/1	upstream: reported C repro on 2020/10/11 20:56
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BUG: KASAN: use-after-free in __lock_acquire+0x2cb4/0x3ff0 kernel/locking/lockdep.c:3294
Read of size 8 at addr ffff8880962c1420 by task syz-executor.5/20683

CPU: 0 PID: 20683 Comm: syz-executor.5 Not tainted 4.19.154-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fc/0x2fe lib/dump_stack.c:118
 print_address_description.cold+0x54/0x219 mm/kasan/report.c:256
 kasan_report_error.cold+0x8a/0x1c7 mm/kasan/report.c:354
 kasan_report mm/kasan/report.c:412 [inline]
 __asan_report_load8_noabort+0x88/0x90 mm/kasan/report.c:433
 __lock_acquire+0x2cb4/0x3ff0 kernel/locking/lockdep.c:3294
 lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3907
 __mutex_lock_common kernel/locking/mutex.c:925 [inline]
 __ww_mutex_lock.constprop.0+0x141/0x2cb0 kernel/locking/mutex.c:1080
 reservation_object_lock include/linux/reservation.h:166 [inline]
 vgem_fence_attach_ioctl+0x3ef/0x640 drivers/gpu/drm/vgem/vgem_fence.c:193
 drm_ioctl_kernel+0x208/0x2a0 drivers/gpu/drm/drm_ioctl.c:757
 drm_ioctl+0x507/0x9c0 drivers/gpu/drm/drm_ioctl.c:857
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0xcdb/0x12e0 fs/ioctl.c:688
 ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45deb9
Code: 0d b4 fb 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 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f70b22b9c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000000c5c0 RCX: 000000000045deb9
RDX: 0000000020000140 RSI: 00000000c10c5541 RDI: 0000000000000004
RBP: 000000000118bf60 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bf2c
R13: 00007ffe4899b09f R14: 00007f70b22ba9c0 R15: 000000000118bf2c

Allocated by task 20683:
 __do_kmalloc mm/slab.c:3727 [inline]
 __kmalloc+0x15a/0x3c0 mm/slab.c:3736
 kmalloc include/linux/slab.h:520 [inline]
 kzalloc include/linux/slab.h:709 [inline]
 dma_buf_export+0x1f1/0xa20 drivers/dma-buf/dma-buf.c:416
 drm_gem_dmabuf_export+0x17/0x80 drivers/gpu/drm/drm_prime.c:365
 drm_gem_prime_export+0x182/0x200 drivers/gpu/drm/drm_prime.c:546
 attach_dmabuf drivers/gpu/drm/vgem/vgem_fence.c:124 [inline]
 vgem_fence_attach_ioctl+0x395/0x640 drivers/gpu/drm/vgem/vgem_fence.c:173
 drm_ioctl_kernel+0x208/0x2a0 drivers/gpu/drm/drm_ioctl.c:757
 drm_ioctl+0x507/0x9c0 drivers/gpu/drm/drm_ioctl.c:857
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0xcdb/0x12e0 fs/ioctl.c:688
 ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 20684:
 __cache_free mm/slab.c:3503 [inline]
 kfree+0xcc/0x210 mm/slab.c:3822
 dma_buf_release+0x329/0x630 drivers/dma-buf/dma-buf.c:80
 __fput+0x2ce/0x890 fs/file_table.c:278
 task_work_run+0x148/0x1c0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:193 [inline]
 exit_to_usermode_loop+0x251/0x2a0 arch/x86/entry/common.c:167
 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:271 [inline]
 do_syscall_64+0x538/0x620 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880962c1240
 which belongs to the cache kmalloc-1024 of size 1024
The buggy address is located 480 bytes inside of
 1024-byte region [ffff8880962c1240, ffff8880962c1640)
The buggy address belongs to the page:
page:ffffea000258b000 count:1 mapcount:0 mapping:ffff88813bff0ac0 index:0x0 compound_mapcount: 0
flags: 0xfff00000008100(slab|head)
raw: 00fff00000008100 ffffea000176c888 ffffea0000f16608 ffff88813bff0ac0
raw: 0000000000000000 ffff8880962c0040 0000000100000007 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880962c1300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880962c1380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880962c1400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff8880962c1480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880962c1500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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