==================================================================
BUG: KASAN: use-after-free in link_path_walk+0x1375/0x1710 fs/namei.c:1949
Read of size 4 at addr ffff8800b9f5d600 by task syz-executor2/2422

CPU: 0 PID: 2422 Comm: syz-executor2 Not tainted 4.4.133-g54f36ea #50
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
binder: 2424:2426 unknown command -2121545979
binder: 2424:2426 ioctl c0306201 20007000 returned -22
binder: 2424:2427 unknown command -2121545979
binder: 2424:2427 ioctl c0306201 20007000 returned -22
 0000000000000000 39b75e06bf7dea7b ffff88009f3ef890 ffffffff81e0e4cd
 ffffea0002e7d700 ffff8800b9f5d600 0000000000000000 ffff8800b9f5d600
 ffff88009f3efc70 ffff88009f3ef8c8 ffffffff815154dc ffff8800b9f5d600
Call Trace:
 [<ffffffff81e0e4cd>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e0e4cd>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff815154dc>] print_address_description+0x6c/0x216 mm/kasan/report.c:252
 [<ffffffff815157fb>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff815157fb>] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408
 [<ffffffff814f92d4>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428
 [<ffffffff8154a6a5>] link_path_walk+0x1375/0x1710 fs/namei.c:1949
 [<ffffffff8154b974>] path_openat+0x1a4/0x3a10 fs/namei.c:3358
 [<ffffffff81551ef7>] do_filp_open+0x197/0x270 fs/namei.c:3393
 [<ffffffff8151b53c>] do_sys_open+0x31c/0x610 fs/open.c:1038
 [<ffffffff81626aed>] C_SYSC_openat fs/compat.c:1101 [inline]
 [<ffffffff81626aed>] compat_SyS_openat+0x2d/0x40 fs/compat.c:1099
 [<ffffffff81006d96>] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline]
 [<ffffffff81006d96>] do_fast_syscall_32+0x326/0x8b0 arch/x86/entry/common.c:459
 [<ffffffff838c28aa>] sysenter_flags_fixed+0xd/0x17

Allocated by task 2422:
 [<ffffffff810341d6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814f83a3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814f8687>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814f8687>] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814f8c52>] kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:554
 [<ffffffff814f474e>] slab_post_alloc_hook mm/slub.c:1349 [inline]
 [<ffffffff814f474e>] slab_alloc_node mm/slub.c:2615 [inline]
 [<ffffffff814f474e>] slab_alloc mm/slub.c:2623 [inline]
 [<ffffffff814f474e>] kmem_cache_alloc+0xbe/0x2a0 mm/slub.c:2628
 [<ffffffff8156a3ce>] __d_alloc+0x2e/0x7b0 fs/dcache.c:1589
 [<ffffffff8156adf7>] d_make_root+0x47/0x90 fs/dcache.c:1934
 [<ffffffff81841c9d>] ramfs_fill_super+0x35d/0x490 fs/ramfs/inode.c:232
 [<ffffffff8152659b>] mount_nodev+0x5b/0x100 fs/super.c:1086
 [<ffffffff8184113c>] ramfs_mount+0x2c/0x40 fs/ramfs/inode.c:242
 [<ffffffff815285cc>] mount_fs+0x28c/0x370 fs/super.c:1146
 [<ffffffff815803e1>] vfs_kern_mount.part.30+0xd1/0x3d0 fs/namespace.c:991
 [<ffffffff81587a2e>] vfs_kern_mount fs/namespace.c:973 [inline]
 [<ffffffff81587a2e>] do_new_mount fs/namespace.c:2517 [inline]
 [<ffffffff81587a2e>] do_mount+0x4ee/0x2860 fs/namespace.c:2833
 [<ffffffff816259aa>] C_SYSC_mount fs/compat.c:824 [inline]
 [<ffffffff816259aa>] compat_SyS_mount+0x57a/0x1040 fs/compat.c:789
 [<ffffffff81006d96>] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline]
 [<ffffffff81006d96>] do_fast_syscall_32+0x326/0x8b0 arch/x86/entry/common.c:459
 [<ffffffff838c28aa>] sysenter_flags_fixed+0xd/0x17

Freed by task 2423:
 [<ffffffff810341d6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814f83a3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814f8cd2>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814f8cd2>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814f5e5e>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814f5e5e>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814f5e5e>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814f5e5e>] kmem_cache_free+0xbe/0x340 mm/slub.c:2881
 [<ffffffff81561b45>] __d_free fs/dcache.c:257 [inline]
 [<ffffffff81561b45>] dentry_free+0xd5/0x150 fs/dcache.c:333
 [<ffffffff81563b8c>] __dentry_kill+0x4ac/0x5f0 fs/dcache.c:576
 [<ffffffff81567467>] dentry_kill fs/dcache.c:603 [inline]
 [<ffffffff81567467>] dput.part.26+0x587/0x760 fs/dcache.c:818
 [<ffffffff815694b3>] dput fs/dcache.c:782 [inline]
 [<ffffffff815694b3>] do_one_tree+0x43/0x50 fs/dcache.c:1473
 [<ffffffff8156a2d2>] shrink_dcache_for_umount+0x62/0x130 fs/dcache.c:1487
 [<ffffffff81523bed>] generic_shutdown_super+0x6d/0x300 fs/super.c:413
 [<ffffffff81524472>] kill_anon_super fs/super.c:914 [inline]
 [<ffffffff81524472>] kill_litter_super+0x72/0x90 fs/super.c:924
 [<ffffffff818410ff>] ramfs_kill_sb+0x3f/0x50 fs/ramfs/inode.c:248
 [<ffffffff8152494d>] deactivate_locked_super+0x8d/0xd0 fs/super.c:301
 [<ffffffff81525291>] deactivate_super+0x91/0xd0 fs/super.c:332
 [<ffffffff8157f692>] cleanup_mnt+0xb2/0x160 fs/namespace.c:1119
 [<ffffffff8157f7c6>] __cleanup_mnt+0x16/0x20 fs/namespace.c:1126
 [<ffffffff8118bc3f>] task_work_run+0x10f/0x190 kernel/task_work.c:115
 [<ffffffff8100362d>] tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 [<ffffffff8100362d>] exit_to_usermode_loop+0x13d/0x160 arch/x86/entry/common.c:252
 [<ffffffff81007090>] prepare_exit_to_usermode arch/x86/entry/common.c:283 [inline]
 [<ffffffff81007090>] syscall_return_slowpath arch/x86/entry/common.c:348 [inline]
 [<ffffffff81007090>] do_syscall_32_irqs_on arch/x86/entry/common.c:398 [inline]
 [<ffffffff81007090>] do_fast_syscall_32+0x620/0x8b0 arch/x86/entry/common.c:459
 [<ffffffff838c28aa>] sysenter_flags_fixed+0xd/0x17

The buggy address belongs to the object at ffff8800b9f5d600
 which belongs to the cache dentry of size 288
The buggy address is located 0 bytes inside of
 288-byte region [ffff8800b9f5d600, ffff8800b9f5d720)
The buggy address belongs to the page:
------------[ cut here ]------------
WARNING: CPU: 1 PID: 2437 at kernel/locking/lockdep.c:973 lock_accessed kernel/locking/lockdep.c:973 [inline]()
WARNING: CPU: 1 PID: 2437 at kernel/locking/lockdep.c:973 __bfs+0x2aa/0x5f0 kernel/locking/lockdep.c:1040()