syzbot

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BUG: KASAN: slab-out-of-bounds in find_first_zero_bit+0xc5/0xe0 lib/find_bit.c:125
Read of size 8 at addr ffff8801d7480a00 by task syzkaller291450/4476

CPU: 1 PID: 4476 Comm: syzkaller291450 Not tainted 4.16.0-rc7+ #8
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x24d lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report+0x23c/0x360 mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 find_first_zero_bit+0xc5/0xe0 lib/find_bit.c:125
 bfs_create+0xf7/0x610 fs/bfs/dir.c:92
 lookup_open+0x1217/0x1970 fs/namei.c:3200
 do_last fs/namei.c:3291 [inline]
 path_openat+0xd76/0x3530 fs/namei.c:3519
 do_filp_open+0x25b/0x3b0 fs/namei.c:3554
 do_sys_open+0x502/0x6d0 fs/open.c:1059
 SYSC_open fs/open.c:1077 [inline]
 SyS_open+0x2d/0x40 fs/open.c:1072
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x4404f9
RSP: 002b:00007ffd2305ebd8 EFLAGS: 00000207 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004404f9
RDX: 0000000000000000 RSI: 0000000000000040 RDI: 0000000020000340
RBP: 0000000000000003 R08: 000000000000000a R09: 6f6f6c2f7665642f
R10: 0000000000000000 R11: 0000000000000207 R12: 0000000000000004
R13: 0000000000401d70 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 4476:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:552
 __do_kmalloc mm/slab.c:3706 [inline]
 __kmalloc+0x162/0x760 mm/slab.c:3715
 kmalloc include/linux/slab.h:517 [inline]
 kzalloc include/linux/slab.h:701 [inline]
 bfs_fill_super+0x3d3/0xea0 fs/bfs/inode.c:362
 mount_bdev+0x2b7/0x370 fs/super.c:1119
 bfs_mount+0x34/0x40 fs/bfs/inode.c:465
 mount_fs+0x66/0x2d0 fs/super.c:1222
 vfs_kern_mount.part.26+0xc6/0x4a0 fs/namespace.c:1037
 vfs_kern_mount fs/namespace.c:2509 [inline]
 do_new_mount fs/namespace.c:2512 [inline]
 do_mount+0xea4/0x2bb0 fs/namespace.c:2842
 SYSC_mount fs/namespace.c:3058 [inline]
 SyS_mount+0xab/0x120 fs/namespace.c:3035
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 2830:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
 __cache_free mm/slab.c:3486 [inline]
 kfree+0xd9/0x260 mm/slab.c:3801
 single_release+0x88/0xb0 fs/seq_file.c:606
 __fput+0x327/0x7e0 fs/file_table.c:209
 ____fput+0x15/0x20 fs/file_table.c:243
 task_work_run+0x199/0x270 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 exit_to_usermode_loop+0x275/0x2f0 arch/x86/entry/common.c:166
 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
 do_syscall_64+0x6ec/0x940 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff8801d7480a00
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 0 bytes inside of
 32-byte region [ffff8801d7480a00, ffff8801d7480a20)
The buggy address belongs to the page:
page:ffffea00075d2000 count:1 mapcount:0 mapping:ffff8801d7480000 index:0xffff8801d7480fc1
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d7480000 ffff8801d7480fc1 000000010000003f
raw: ffffea00075d1ea0 ffffea00075d32a0 ffff8801dac001c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d7480900: 00 02 fc fc fc fc fc fc 00 02 fc fc fc fc fc fc
 ffff8801d7480980: 00 02 fc fc fc fc fc fc 00 fc fc fc fc fc fc fc
>ffff8801d7480a00: 07 fc fc fc fc fc fc fc fb fb fb fb fc fc fc fc
                   ^
 ffff8801d7480a80: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
 ffff8801d7480b00: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
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