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BUG: KASAN: use-after-free in do_new_mount_fc fs/namespace.c:2770 [inline]
BUG: KASAN: use-after-free in do_new_mount fs/namespace.c:2824 [inline]
BUG: KASAN: use-after-free in do_mount+0x19a7/0x1bd0 fs/namespace.c:3142
Read of size 8 at addr ffff88808ba7b968 by task syz-executor.4/4471

CPU: 0 PID: 4471 Comm: syz-executor.4 Not tainted 5.3.0-rc6+ #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+0x113/0x167 lib/dump_stack.c:113
 print_address_description.cold.8+0x9/0x318 mm/kasan/report.c:351
 __kasan_report.cold.9+0x1b/0x3f mm/kasan/report.c:482
 kasan_report+0x12/0x17 mm/kasan/common.c:618
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
 do_new_mount_fc fs/namespace.c:2770 [inline]
 do_new_mount fs/namespace.c:2824 [inline]
 do_mount+0x19a7/0x1bd0 fs/namespace.c:3142
 ksys_mount+0xba/0xe0 fs/namespace.c:3351
 __do_sys_mount fs/namespace.c:3365 [inline]
 __se_sys_mount fs/namespace.c:3362 [inline]
 __x64_sys_mount+0xb9/0x150 fs/namespace.c:3362
 do_syscall_64+0xd0/0x540 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459a59
Code: fd b7 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 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f6fe32d6c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000459a59
RDX: 0000000020000a40 RSI: 00000000200005c0 RDI: 0000000000000000
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f6fe32d76d4
R13: 00000000004c6291 R14: 00000000004db2f8 R15: 00000000ffffffff

Allocated by task 4471:
 save_stack+0x21/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 __kasan_kmalloc.constprop.9+0xc7/0xd0 mm/kasan/common.c:493
 kasan_slab_alloc+0x12/0x20 mm/kasan/common.c:501
 slab_post_alloc_hook mm/slab.h:520 [inline]
 slab_alloc mm/slab.c:3319 [inline]
 kmem_cache_alloc+0x121/0x750 mm/slab.c:3483
 kmem_cache_zalloc include/linux/slab.h:738 [inline]
 alloc_vfsmnt+0x21/0x620 fs/namespace.c:177
 vfs_create_mount+0x8a/0x4b0 fs/namespace.c:940
 do_new_mount_fc fs/namespace.c:2760 [inline]
 do_new_mount fs/namespace.c:2824 [inline]
 do_mount+0x14c1/0x1bd0 fs/namespace.c:3142
 ksys_mount+0xba/0xe0 fs/namespace.c:3351
 __do_sys_mount fs/namespace.c:3365 [inline]
 __se_sys_mount fs/namespace.c:3362 [inline]
 __x64_sys_mount+0xb9/0x150 fs/namespace.c:3362
 do_syscall_64+0xd0/0x540 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 4481:
 save_stack+0x21/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:455
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:463
 __cache_free mm/slab.c:3425 [inline]
 kmem_cache_free+0x83/0x320 mm/slab.c:3693
 free_vfsmnt+0x62/0x80 fs/namespace.c:554
 delayed_free_vfsmnt+0xd/0x10 fs/namespace.c:559
 __rcu_reclaim kernel/rcu/rcu.h:222 [inline]
 rcu_do_batch kernel/rcu/tree.c:2114 [inline]
 rcu_core+0x65e/0x14c0 kernel/rcu/tree.c:2314
 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2323
 __do_softirq+0x262/0x9a8 kernel/softirq.c:292

The buggy address belongs to the object at ffff88808ba7b940
 which belongs to the cache mnt_cache of size 312
The buggy address is located 40 bytes inside of
 312-byte region [ffff88808ba7b940, ffff88808ba7ba78)
The buggy address belongs to the page:
page:ffffea00022e9ec0 refcount:1 mapcount:0 mapping:ffff8880aa593a80 index:0xffff88808ba7bdc0
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea000265f388 ffffea00028674c8 ffff8880aa593a80
raw: ffff88808ba7bdc0 ffff88808ba7b040 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808ba7b800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808ba7b880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc
>ffff88808ba7b900: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                                          ^
 ffff88808ba7b980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808ba7ba00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc
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