syzbot

device gre0 entered promiscuous mode
kasan: CONFIG_KASAN_INLINE enabled
==================================================================
BUG: KASAN: use-after-free in __fcheck_files include/linux/fdtable.h:85 [inline]
BUG: KASAN: use-after-free in fcheck_files include/linux/fdtable.h:95 [inline]
BUG: KASAN: use-after-free in __fget+0x547/0x570 fs/file.c:690
Read of size 4 at addr ffff8801d4302f00 by task syz-executor4/22370

CPU: 0 PID: 22370 Comm: syz-executor4 Not tainted 4.15.0-rc5+ #147
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+0x194/0x257 lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:429
 __fcheck_files include/linux/fdtable.h:85 [inline]
 fcheck_files include/linux/fdtable.h:95 [inline]
 __fget+0x547/0x570 fs/file.c:690
 __fget_light+0x2eb/0x380 fs/file.c:745
 __fdget+0x18/0x20 fs/file.c:753
 fdget include/linux/file.h:57 [inline]
 sockfd_lookup_light+0x21/0x150 net/socket.c:495
 SYSC_sendto+0x144/0x5c0 net/socket.c:1709
 SyS_sendto+0x40/0x50 net/socket.c:1695
 do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
 do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
 entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:125
RIP: 0023:0xf7f53c79
RSP: 002b:00000000f772e08c EFLAGS: 00000296 ORIG_RAX: 0000000000000171
RAX: ffffffffffffffda RBX: 0000000000000013 RCX: 0000000020ab7000
RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000020ab8000
RBP: 000000000000001c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 22368:
 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:551
 __do_kmalloc mm/slab.c:3708 [inline]
 __kmalloc+0x162/0x760 mm/slab.c:3717
 kmalloc include/linux/slab.h:504 [inline]
 kzalloc include/linux/slab.h:688 [inline]
 ext4_htree_store_dirent+0x8b/0x580 fs/ext4/dir.c:451
 htree_dirblock_to_tree+0x4e8/0xa00 fs/ext4/namei.c:1019
 ext4_htree_fill_tree+0x2bb/0xcb0 fs/ext4/namei.c:1096
 ext4_dx_readdir fs/ext4/dir.c:575 [inline]
 ext4_readdir+0x1d03/0x3050 fs/ext4/dir.c:122
 iterate_dir+0x1ca/0x530 fs/readdir.c:51
 SYSC_getdents fs/readdir.c:231 [inline]
 SyS_getdents+0x225/0x450 fs/readdir.c:212
 entry_SYSCALL_64_fastpath+0x1f/0x96

Freed by task 22368:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3488 [inline]
 kfree+0xd6/0x260 mm/slab.c:3803
 free_rb_tree_fname+0x85/0xe0 fs/ext4/dir.c:403
 ext4_htree_free_dir_info fs/ext4/dir.c:425 [inline]
 ext4_release_dir+0x44/0x60 fs/ext4/dir.c:623
 __fput+0x327/0x7e0 fs/file_table.c:210
 ____fput+0x15/0x20 fs/file_table.c:244
 task_work_run+0x199/0x270 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 exit_to_usermode_loop+0x296/0x310 arch/x86/entry/common.c:162
 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
 syscall_return_slowpath+0x490/0x550 arch/x86/entry/common.c:264
 entry_SYSCALL_64_fastpath+0x94/0x96

The buggy address belongs to the object at ffff8801d4302f00
 which belongs to the cache kmalloc-64 of size 64
The buggy address is located 0 bytes inside of
 64-byte region [ffff8801d4302f00, ffff8801d4302f40)
The buggy address belongs to the page:
page:0000000089700587 count:1 mapcount:0 mapping:00000000159189cf index:0xffff8801d4302400
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d4302000 ffff8801d4302400 000000010000001b
raw: ffffea00070cfda0 ffffea0006cb16e0 ffff8801db000340 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d4302e00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff8801d4302e80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff8801d4302f00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
                   ^
 ffff8801d4302f80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff8801d4303000: 00 00 00 00 fc fc fc fc 00 00 00 fc fc fc fc fc
==================================================================