==================================================================
BUG: KASAN: use-after-free in link_path_walk+0x1375/0x1710 fs/namei.c:1949
Read of size 4 at addr ffff8801d2ef4b00 by task syz-executor6/11064

CPU: 0 PID: 11064 Comm: syz-executor6 Not tainted 4.4.133-g3f51ea2 #49
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 bc4c2399f1f332d2 ffff8801baeb7890 ffffffff81e0e4cd
 ffffea00074bbd00 ffff8801d2ef4b00 0000000000000000 ffff8801d2ef4b00
 ffff8801baeb7c70 ffff8801baeb78c8 ffffffff815154cc ffff8801d2ef4b00
Call Trace:
 [<ffffffff81e0e4cd>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e0e4cd>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff815154cc>] print_address_description+0x6c/0x216 mm/kasan/report.c:252
 [<ffffffff815157eb>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff815157eb>] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408
 [<ffffffff814f92c4>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428
 [<ffffffff8154a695>] link_path_walk+0x1375/0x1710 fs/namei.c:1949
 [<ffffffff8154b964>] path_openat+0x1a4/0x3a10 fs/namei.c:3358
 [<ffffffff81551ee7>] do_filp_open+0x197/0x270 fs/namei.c:3393
 [<ffffffff8151b52c>] do_sys_open+0x31c/0x610 fs/open.c:1038
 [<ffffffff81626add>] C_SYSC_openat fs/compat.c:1101 [inline]
 [<ffffffff81626add>] 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 11054:
 [<ffffffff810341d6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814f8393>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814f8677>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814f8677>] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814f8c42>] kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:554
 [<ffffffff814f473e>] slab_post_alloc_hook mm/slub.c:1349 [inline]
 [<ffffffff814f473e>] slab_alloc_node mm/slub.c:2615 [inline]
 [<ffffffff814f473e>] slab_alloc mm/slub.c:2623 [inline]
 [<ffffffff814f473e>] kmem_cache_alloc+0xbe/0x2a0 mm/slub.c:2628
 [<ffffffff8156a3be>] __d_alloc+0x2e/0x7b0 fs/dcache.c:1589
 [<ffffffff8156ade7>] d_make_root+0x47/0x90 fs/dcache.c:1934
 [<ffffffff81841c8d>] ramfs_fill_super+0x35d/0x490 fs/ramfs/inode.c:232
 [<ffffffff8152658b>] mount_nodev+0x5b/0x100 fs/super.c:1086
 [<ffffffff8184112c>] ramfs_mount+0x2c/0x40 fs/ramfs/inode.c:242
 [<ffffffff815285bc>] mount_fs+0x28c/0x370 fs/super.c:1146
 [<ffffffff815803d1>] vfs_kern_mount.part.30+0xd1/0x3d0 fs/namespace.c:991
 [<ffffffff81587a1e>] vfs_kern_mount fs/namespace.c:973 [inline]
 [<ffffffff81587a1e>] do_new_mount fs/namespace.c:2517 [inline]
 [<ffffffff81587a1e>] do_mount+0x4ee/0x2860 fs/namespace.c:2833
 [<ffffffff8162599a>] C_SYSC_mount fs/compat.c:824 [inline]
 [<ffffffff8162599a>] 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 11063:
 [<ffffffff810341d6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814f8393>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814f8cc2>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814f8cc2>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814f5e4e>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814f5e4e>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814f5e4e>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814f5e4e>] kmem_cache_free+0xbe/0x340 mm/slub.c:2881
 [<ffffffff81561b35>] __d_free fs/dcache.c:257 [inline]
 [<ffffffff81561b35>] dentry_free+0xd5/0x150 fs/dcache.c:333
 [<ffffffff81563b7c>] __dentry_kill+0x4ac/0x5f0 fs/dcache.c:576
 [<ffffffff81567457>] dentry_kill fs/dcache.c:603 [inline]
 [<ffffffff81567457>] dput.part.26+0x587/0x760 fs/dcache.c:818
 [<ffffffff815694a3>] dput fs/dcache.c:782 [inline]
 [<ffffffff815694a3>] do_one_tree+0x43/0x50 fs/dcache.c:1473
 [<ffffffff8156a2c2>] shrink_dcache_for_umount+0x62/0x130 fs/dcache.c:1487
 [<ffffffff81523bdd>] generic_shutdown_super+0x6d/0x300 fs/super.c:413
 [<ffffffff81524462>] kill_anon_super fs/super.c:914 [inline]
 [<ffffffff81524462>] kill_litter_super+0x72/0x90 fs/super.c:924
 [<ffffffff818410ef>] ramfs_kill_sb+0x3f/0x50 fs/ramfs/inode.c:248
 [<ffffffff8152493d>] deactivate_locked_super+0x8d/0xd0 fs/super.c:301
 [<ffffffff81525281>] deactivate_super+0x91/0xd0 fs/super.c:332
 [<ffffffff8157f682>] cleanup_mnt+0xb2/0x160 fs/namespace.c:1119
 [<ffffffff8157f7b6>] __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 ffff8801d2ef4b00
 which belongs to the cache dentry of size 288
The buggy address is located 0 bytes inside of
 288-byte region [ffff8801d2ef4b00, ffff8801d2ef4c20)
The buggy address belongs to the page:
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory accessgeneral protection fault: 0000 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 11083 Comm: modprobe Not tainted 4.4.133-g3f51ea2 #49
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800b5bab000 task.stack: ffff8801d0590000
RIP: 0010:[<ffffffff8122f461>]  [<ffffffff8122f461>] __lock_acquire+0x5a1/0x5270 kernel/locking/lockdep.c:3092
RSP: 0018:ffff8801d0597860  EFLAGS: 00010006
RAX: dffffc0000000000 RBX: 0000000000000001 RCX: 0000000000000000
RDX: 0000000000000003 RSI: 0000000000000000 RDI: 0000000000000018
RBP: ffff8801d05979f8 R08: 0000000000000001 R09: 0000000000000000
R10: ffffffff83a44860 R11: ffff8800b5bab000 R12: 0000000000000000
R13: 0000000000000018 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000081410f4 CR3: 00000001d7f72000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8800b5bab928 ffff8800b5bab8e0 1ffff1003a0b2f10 ffff8800b5bab908
 00000000000000c3 ffff8800b5bab92a ffff8800b5bab929 0000000000000000
 ffff8801d0597a48 0000000000000046 ffff8800b5bab8f8 ffffffff853cef80
Call Trace:
 [<ffffffff8123590e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff838c0086>] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline]
 [<ffffffff838c0086>] _raw_spin_lock+0x36/0x50 kernel/locking/spinlock.c:151
 [<ffffffff814954fc>] spin_lock include/linux/spinlock.h:302 [inline]
 [<ffffffff814954fc>] zap_pte_range mm/memory.c:1128 [inline]
 [<ffffffff814954fc>] zap_pmd_range mm/memory.c:1262 [inline]
 [<ffffffff814954fc>] zap_pud_range mm/memory.c:1283 [inline]
 [<ffffffff814954fc>] unmap_page_range mm/memory.c:1307 [inline]
 [<ffffffff814954fc>] unmap_single_vma+0x82c/0x1250 mm/memory.c:1352
 [<ffffffff81497a41>] unmap_vmas+0x81/0xd0 mm/memory.c:1382
 [<ffffffff814aff19>] exit_mmap+0x1c9/0x3a0 mm/mmap.c:2926
 [<ffffffff811253f8>] __mmput kernel/fork.c:715 [inline]
 [<ffffffff811253f8>] mmput+0xf8/0x2d0 kernel/fork.c:735
 [<ffffffff81135068>] exit_mm kernel/exit.c:444 [inline]
 [<ffffffff81135068>] do_exit+0x8d8/0x26b0 kernel/exit.c:746
 [<ffffffff811721a8>] call_usermodehelper_exec_async+0x3a8/0x4d0 kernel/kmod.c:265
 [<ffffffff838c1395>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:510
Code: 25 28 00 00 00 0f 85 91 35 00 00 48 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f 5d c3 48 b8 00 00 00 00 00 fc ff df 4c 89 ea 48 c1 ea 03 <80> 3c 02 00 0f 85 a4 36 00 00 49 81 7d 00 20 19 c5 84 0f 84 83 
RIP  [<ffffffff8122f461>] __lock_acquire+0x5a1/0x5270 kernel/locking/lockdep.c:3092
 RSP <ffff8801d0597860>
---[ end trace 4c743fb4ffaff331 ]---