==================================================================
BUG: KASAN: use-after-free in link_path_walk+0x1375/0x1710 fs/namei.c:1949
Read of size 4 at addr ffff8800ab77c580 by task syz-executor4/27839

CPU: 0 PID: 27839 Comm: syz-executor4 Not tainted 4.4.135-ge75204c #53
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 1d36609de2a4dc95 ffff8800b957f8a0 ffffffff81e0ed0d
 ffffea0002addf00 ffff8800ab77c580 0000000000000000 ffff8800ab77c580
 ffff8800b957fc80 ffff8800b957f8d8 ffffffff81515946 ffff8800ab77c580
Call Trace:
 [<ffffffff81e0ed0d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e0ed0d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff81515946>] print_address_description+0x6c/0x216 mm/kasan/report.c:252
 [<ffffffff81515c65>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff81515c65>] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408
netlink: 19 bytes leftover after parsing attributes in process `syz-executor3'.
netlink: 19 bytes leftover after parsing attributes in process `syz-executor3'.
 [<ffffffff814f9734>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428
 [<ffffffff8154ab15>] link_path_walk+0x1375/0x1710 fs/namei.c:1949
 [<ffffffff8154bde4>] path_openat+0x1a4/0x3a10 fs/namei.c:3358
 [<ffffffff81552367>] do_filp_open+0x197/0x270 fs/namei.c:3393
 [<ffffffff8151b9ac>] do_sys_open+0x31c/0x610 fs/open.c:1038
 [<ffffffff8162709a>] C_SYSC_open fs/compat.c:1092 [inline]
 [<ffffffff8162709a>] compat_SyS_open+0x2a/0x40 fs/compat.c:1090
 [<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
 [<ffffffff838c40aa>] sysenter_flags_fixed+0xd/0x17

Allocated by task 27826:
 [<ffffffff810341d6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814f8803>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814f8ae7>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814f8ae7>] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814f90b2>] kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:554
 [<ffffffff814f4bae>] slab_post_alloc_hook mm/slub.c:1349 [inline]
 [<ffffffff814f4bae>] slab_alloc_node mm/slub.c:2615 [inline]
 [<ffffffff814f4bae>] slab_alloc mm/slub.c:2623 [inline]
 [<ffffffff814f4bae>] kmem_cache_alloc+0xbe/0x2a0 mm/slub.c:2628
 [<ffffffff8156a9be>] __d_alloc+0x2e/0x7b0 fs/dcache.c:1589
 [<ffffffff8156b3e7>] d_make_root+0x47/0x90 fs/dcache.c:1956
 [<ffffffff818425bd>] ramfs_fill_super+0x35d/0x490 fs/ramfs/inode.c:232
 [<ffffffff81526a0b>] mount_nodev+0x5b/0x100 fs/super.c:1086
 [<ffffffff81841a5c>] ramfs_mount+0x2c/0x40 fs/ramfs/inode.c:242
 [<ffffffff81528a3c>] mount_fs+0x28c/0x370 fs/super.c:1146
 [<ffffffff815809d1>] vfs_kern_mount.part.30+0xd1/0x3d0 fs/namespace.c:991
 [<ffffffff8158801e>] vfs_kern_mount fs/namespace.c:973 [inline]
 [<ffffffff8158801e>] do_new_mount fs/namespace.c:2517 [inline]
 [<ffffffff8158801e>] do_mount+0x4ee/0x2860 fs/namespace.c:2833
 [<ffffffff81625f9a>] C_SYSC_mount fs/compat.c:824 [inline]
 [<ffffffff81625f9a>] 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
 [<ffffffff838c40aa>] sysenter_flags_fixed+0xd/0x17

Freed by task 27826:
 [<ffffffff810341d6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814f8803>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814f9132>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814f9132>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814f62be>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814f62be>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814f62be>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814f62be>] kmem_cache_free+0xbe/0x340 mm/slub.c:2881
 [<ffffffff81561fb5>] __d_free fs/dcache.c:257 [inline]
 [<ffffffff81561fb5>] dentry_free+0xd5/0x150 fs/dcache.c:333
 [<ffffffff8156417c>] __dentry_kill+0x4ac/0x5f0 fs/dcache.c:576
 [<ffffffff81567a57>] dentry_kill fs/dcache.c:603 [inline]
 [<ffffffff81567a57>] dput.part.26+0x587/0x760 fs/dcache.c:818
 [<ffffffff81569aa3>] dput fs/dcache.c:782 [inline]
 [<ffffffff81569aa3>] do_one_tree+0x43/0x50 fs/dcache.c:1473
 [<ffffffff8156a8c2>] shrink_dcache_for_umount+0x62/0x130 fs/dcache.c:1487
 [<ffffffff8152405d>] generic_shutdown_super+0x6d/0x300 fs/super.c:413
 [<ffffffff815248e2>] kill_anon_super fs/super.c:914 [inline]
 [<ffffffff815248e2>] kill_litter_super+0x72/0x90 fs/super.c:924
 [<ffffffff81841a1f>] ramfs_kill_sb+0x3f/0x50 fs/ramfs/inode.c:248
 [<ffffffff81524dbd>] deactivate_locked_super+0x8d/0xd0 fs/super.c:301
 [<ffffffff81525701>] deactivate_super+0x91/0xd0 fs/super.c:332
 [<ffffffff8157fc82>] cleanup_mnt+0xb2/0x160 fs/namespace.c:1119
 [<ffffffff8157fdb6>] __cleanup_mnt+0x16/0x20 fs/namespace.c:1126
 [<ffffffff8118bd7f>] 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
 [<ffffffff838c40aa>] sysenter_flags_fixed+0xd/0x17

The buggy address belongs to the object at ffff8800ab77c580
 which belongs to the cache dentry of size 288
The buggy address is located 0 bytes inside of
 288-byte region [ffff8800ab77c580, ffff8800ab77c6a0)
The buggy address belongs to the page:
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access[  631.588215] ------------[ cut here ]------------
WARNING: CPU: 1 PID: 3913 at kernel/sched/core.c:7950 __might_sleep+0x138/0x1a0 kernel/sched/core.c:7945()
do not call blocking ops when !TASK_RUNNING; state=1 set at [<ffffffff8113a7fe>] do_wait+0x26e/0xa30 kernel/exit.c:1507