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SubjectKASAN: use-after-free Read in drm_gem_object_release
From
Hello,

syzbot found the following crash on:

HEAD commit: bd6bf7c10484 Merge tag 'pci-v4.20-changes' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1448a683400000
kernel config: https://syzkaller.appspot.com/x/.config?x=2dd8629d56664133
dashboard link: https://syzkaller.appspot.com/bug?extid=e73f2fb5ed5a5df36d33
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11331de5400000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1334e64d400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e73f2fb5ed5a5df36d33@syzkaller.appspotmail.com

drm_mode_create_dumb+0x28d/0x310 drivers/gpu/drm/drm_dumb_buffers.c:92
drm_mode_create_dumb_ioctl+0x25/0x30 drivers/gpu/drm/drm_dumb_buffers.c:98
drm_ioctl_kernel+0x245/0x2f0 drivers/gpu/drm/drm_ioctl.c:751
drm_ioctl+0x57a/0xb20 drivers/gpu/drm/drm_ioctl.c:847
==================================================================
BUG: KASAN: use-after-free in drm_gem_object_release+0xf1/0x110
drivers/gpu/drm/drm_gem.c:813
Read of size 8 at addr ffff8801d83d3410 by task syz-executor977/6742

vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
__do_sys_ioctl fs/ioctl.c:709 [inline]
__se_sys_ioctl fs/ioctl.c:707 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x445989
Code: e8 4c e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 6b c8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffcf076f4e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ffcf076f500 RCX: 0000000000445989
RDX: 0000000020000000 RSI: ffffffffffffffb2 RDI: 0000000000000003
RBP: 0000000000000004 R08: 0000000000000001 R09: 0000000000000100
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: ffffffffffffffff R14: 0000000000000000 R15: 0000000000000000
CPU: 0 PID: 6742 Comm: syz-executor977 Not tainted 4.19.0+ #80
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+0x244/0x39d lib/dump_stack.c:113
print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
drm_gem_object_release+0xf1/0x110 drivers/gpu/drm/drm_gem.c:813
__vgem_gem_destroy drivers/gpu/drm/vgem/vgem_drv.c:175 [inline]
vgem_gem_create drivers/gpu/drm/vgem/vgem_drv.c:199 [inline]
vgem_gem_dumb_create+0x1f8/0x260 drivers/gpu/drm/vgem/vgem_drv.c:214
drm_mode_create_dumb+0x28d/0x310 drivers/gpu/drm/drm_dumb_buffers.c:92
drm_mode_create_dumb_ioctl+0x25/0x30 drivers/gpu/drm/drm_dumb_buffers.c:98
drm_ioctl_kernel+0x245/0x2f0 drivers/gpu/drm/drm_ioctl.c:751
drm_ioctl+0x57a/0xb20 drivers/gpu/drm/drm_ioctl.c:847
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
__do_sys_ioctl fs/ioctl.c:709 [inline]
__se_sys_ioctl fs/ioctl.c:707 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x445989
Code: e8 4c e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 6b c8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffcf076f4e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ffcf076f500 RCX: 0000000000445989
RDX: 0000000020000000 RSI: ffffffffffffffb2 RDI: 0000000000000003
RBP: 0000000000000004 R08: 0000000000000001 R09: 0000000000000100
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: ffffffffffffffff R14: 0000000000000000 R15: 0000000000000000

Allocated by task 6742:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
kmem_cache_alloc_trace+0x152/0x750 mm/slab.c:3620
kmalloc include/linux/slab.h:513 [inline]
kzalloc include/linux/slab.h:707 [inline]
__vgem_gem_create+0x4c/0x100 drivers/gpu/drm/vgem/vgem_drv.c:158
vgem_gem_create drivers/gpu/drm/vgem/vgem_drv.c:187 [inline]
vgem_gem_dumb_create+0xce/0x260 drivers/gpu/drm/vgem/vgem_drv.c:214
drm_mode_create_dumb+0x28d/0x310 drivers/gpu/drm/drm_dumb_buffers.c:92
drm_mode_create_dumb_ioctl+0x25/0x30 drivers/gpu/drm/drm_dumb_buffers.c:98
drm_ioctl_kernel+0x245/0x2f0 drivers/gpu/drm/drm_ioctl.c:751
drm_ioctl+0x57a/0xb20 drivers/gpu/drm/drm_ioctl.c:847
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
__do_sys_ioctl fs/ioctl.c:709 [inline]
__se_sys_ioctl fs/ioctl.c:707 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 6742:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kfree+0xcf/0x230 mm/slab.c:3813
vgem_gem_free_object+0xb6/0xe0 drivers/gpu/drm/vgem/vgem_drv.c:61
drm_gem_object_free+0xf1/0x2b0 drivers/gpu/drm/drm_gem.c:839
kref_put include/linux/kref.h:70 [inline]
drm_gem_object_put_unlocked+0x14c/0x180 drivers/gpu/drm/drm_gem.c:895
vgem_gem_create drivers/gpu/drm/vgem/vgem_drv.c:192 [inline]
vgem_gem_dumb_create+0x120/0x260 drivers/gpu/drm/vgem/vgem_drv.c:214
drm_mode_create_dumb+0x28d/0x310 drivers/gpu/drm/drm_dumb_buffers.c:92
drm_mode_create_dumb_ioctl+0x25/0x30 drivers/gpu/drm/drm_dumb_buffers.c:98
drm_ioctl_kernel+0x245/0x2f0 drivers/gpu/drm/drm_ioctl.c:751
drm_ioctl+0x57a/0xb20 drivers/gpu/drm/drm_ioctl.c:847
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
__do_sys_ioctl fs/ioctl.c:709 [inline]
__se_sys_ioctl fs/ioctl.c:707 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801d83d3300
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 272 bytes inside of
512-byte region [ffff8801d83d3300, ffff8801d83d3500)
The buggy address belongs to the page:
page:ffffea000760f4c0 count:1 mapcount:0 mapping:ffff8801da800940 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea0007473948 ffffea0007471dc8 ffff8801da800940
raw: 0000000000000000 ffff8801d83d3080 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801d83d3300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801d83d3380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8801d83d3400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8801d83d3480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801d83d3500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
==================================================================
CPU: 0 PID: 6778 Comm: syz-executor977 Tainted: G B 4.19.0+
#80
BUG: KASAN: double-free or invalid-free in __vgem_gem_destroy
drivers/gpu/drm/vgem/vgem_drv.c:176 [inline]
BUG: KASAN: double-free or invalid-free in vgem_gem_create
drivers/gpu/drm/vgem/vgem_drv.c:199 [inline]
BUG: KASAN: double-free or invalid-free in vgem_gem_dumb_create+0x203/0x260
drivers/gpu/drm/vgem/vgem_drv.c:214
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+0x244/0x39d lib/dump_stack.c:113
fail_dump lib/fault-inject.c:51 [inline]
should_fail.cold.4+0xa/0x17 lib/fault-inject.c:149
__should_failslab+0x124/0x180 mm/failslab.c:32
should_failslab+0x9/0x14 mm/slab_common.c:1557
slab_pre_alloc_hook mm/slab.h:423 [inline]
slab_alloc mm/slab.c:3378 [inline]
kmem_cache_alloc_trace+0x2d7/0x750 mm/slab.c:3618
kmalloc include/linux/slab.h:513 [inline]
drm_vma_node_allow+0x5f/0x290 drivers/gpu/drm/drm_vma_manager.c:277
drm_gem_handle_create_tail+0x233/0x440 drivers/gpu/drm/drm_gem.c:409
drm_gem_handle_create+0x52/0x60 drivers/gpu/drm/drm_gem.c:452
vgem_gem_create drivers/gpu/drm/vgem/vgem_drv.c:191 [inline]
vgem_gem_dumb_create+0x115/0x260 drivers/gpu/drm/vgem/vgem_drv.c:214
drm_mode_create_dumb+0x28d/0x310 drivers/gpu/drm/drm_dumb_buffers.c:92
drm_mode_create_dumb_ioctl+0x25/0x30 drivers/gpu/drm/drm_dumb_buffers.c:98
drm_ioctl_kernel+0x245/0x2f0 drivers/gpu/drm/drm_ioctl.c:751
drm_ioctl+0x57a/0xb20 drivers/gpu/drm/drm_ioctl.c:847
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
__do_sys_ioctl fs/ioctl.c:709 [inline]
__se_sys_ioctl fs/ioctl.c:707 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x445989
Code: e8 4c e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 6b c8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffcf076f4e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ffcf076f500 RCX: 0000000000445989
RDX: 0000000020000000 RSI: ffffffffffffffb2 RDI: 0000000000000003
RBP: 0000000000000004 R08: 0000000000000001 R09: 0000000000000100
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: ffffffffffffffff R14: 0000000000000000 R15: 0000000000000000
CPU: 1 PID: 6767 Comm: syz-executor977 Tainted: G B 4.19.0+
#80
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+0x244/0x39d lib/dump_stack.c:113
print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
kasan_report_invalid_free+0x64/0xa0 mm/kasan/report.c:336
__kasan_slab_free+0x13a/0x150 mm/kasan/kasan.c:501
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kfree+0xcf/0x230 mm/slab.c:3813
__vgem_gem_destroy drivers/gpu/drm/vgem/vgem_drv.c:176 [inline]
vgem_gem_create drivers/gpu/drm/vgem/vgem_drv.c:199 [inline]
vgem_gem_dumb_create+0x203/0x260 drivers/gpu/drm/vgem/vgem_drv.c:214
drm_mode_create_dumb+0x28d/0x310 drivers/gpu/drm/drm_dumb_buffers.c:92
drm_mode_create_dumb_ioctl+0x25/0x30 drivers/gpu/drm/drm_dumb_buffers.c:98
drm_ioctl_kernel+0x245/0x2f0 drivers/gpu/drm/drm_ioctl.c:751
drm_ioctl+0x57a/0xb20 drivers/gpu/drm/drm_ioctl.c:847
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
__do_sys_ioctl fs/ioctl.c:709 [inline]
__se_sys_ioctl fs/ioctl.c:707 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x445989
Code: e8 4c e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 6b c8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffcf076f4e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ffcf076f500 RCX: 0000000000445989
RDX: 0000000020000000 RSI: ffffffffffffffb2 RDI: 0000000000000003
RBP: 0000000000000004 R08: 0000000000000001 R09: 0000000000000100
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: ffffffffffffffff R14: 0000000000000000 R15: 0000000000000000

Allocated by task 6767:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
kmem_cache_alloc_trace+0x152/0x750 mm/slab.c:3620
kmalloc include/linux/slab.h:513 [inline]
kzalloc include/linux/slab.h:707 [inline]
__vgem_gem_create+0x4c/0x100 drivers/gpu/drm/vgem/vgem_drv.c:158
vgem_gem_create drivers/gpu/drm/vgem/vgem_drv.c:187 [inline]
vgem_gem_dumb_create+0xce/0x260 drivers/gpu/drm/vgem/vgem_drv.c:214
drm_mode_create_dumb+0x28d/0x310 drivers/gpu/drm/drm_dumb_buffers.c:92
drm_mode_create_dumb_ioctl+0x25/0x30 drivers/gpu/drm/drm_dumb_buffers.c:98
drm_ioctl_kernel+0x245/0x2f0 drivers/gpu/drm/drm_ioctl.c:751
drm_ioctl+0x57a/0xb20 drivers/gpu/drm/drm_ioctl.c:847
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
__do_sys_ioctl fs/ioctl.c:709 [inline]
__se_sys_ioctl fs/ioctl.c:707 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 6767:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kfree+0xcf/0x230 mm/slab.c:3813
vgem_gem_free_object+0xb6/0xe0 drivers/gpu/drm/vgem/vgem_drv.c:61
drm_gem_object_free+0xf1/0x2b0 drivers/gpu/drm/drm_gem.c:839
kref_put include/linux/kref.h:70 [inline]
drm_gem_object_put_unlocked+0x14c/0x180 drivers/gpu/drm/drm_gem.c:895
vgem_gem_create drivers/gpu/drm/vgem/vgem_drv.c:192 [inline]
vgem_gem_dumb_create+0x120/0x260 drivers/gpu/drm/vgem/vgem_drv.c:214
drm_mode_create_dumb+0x28d/0x310 drivers/gpu/drm/drm_dumb_buffers.c:92
drm_mode_create_dumb_ioctl+0x25/0x30 drivers/gpu/drm/drm_dumb_buffers.c:98
drm_ioctl_kernel+0x245/0x2f0 drivers/gpu/drm/drm_ioctl.c:751
drm_ioctl+0x57a/0xb20 drivers/gpu/drm/drm_ioctl.c:847
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
__do_sys_ioctl fs/ioctl.c:709 [inline]
__se_sys_ioctl fs/ioctl.c:707 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801d4974080
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
512-byte region [ffff8801d4974080, ffff8801d4974280)
The buggy address belongs to the page:
page:ffffea0007525d00 count:1 mapcount:0 mapping:ffff8801da800940 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea0007558e48 ffffea00071d0508 ffff8801da800940
raw: 0000000000000000 ffff8801d4974080 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801d4973f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8801d4974000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8801d4974080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8801d4974100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801d4974180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

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