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BUG: KASAN: use-after-free in css_task_iter_advance+0x49b/0x540 kernel/cgroup/cgroup.c:4507
Read of size 4 at addr ffff8880997c6fdc by task syz-executor.2/26594

CPU: 0 PID: 26594 Comm: syz-executor.2 Not tainted 5.2.0-rc3-next-20190606 #10
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+0x172/0x1f0 lib/dump_stack.c:113
 print_address_description.cold+0xd4/0x306 mm/kasan/report.c:351
 __kasan_report.cold+0x1b/0x36 mm/kasan/report.c:482
 kasan_report+0x12/0x20 mm/kasan/common.c:614
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/generic_report.c:131
 css_task_iter_advance+0x49b/0x540 kernel/cgroup/cgroup.c:4507
 css_task_iter_start+0x18b/0x230 kernel/cgroup/cgroup.c:4543
 pidlist_array_load+0x181/0xa80 kernel/cgroup/cgroup-v1.c:372
 cgroup_pidlist_start+0x37e/0x4c0 kernel/cgroup/cgroup-v1.c:442
 cgroup_seqfile_start+0xa4/0xd0 kernel/cgroup/cgroup.c:3752
 kernfs_seq_start+0xdc/0x190 fs/kernfs/file.c:118
 seq_read+0x2a7/0x1110 fs/seq_file.c:224
 kernfs_fop_read+0xed/0x560 fs/kernfs/file.c:252
 do_loop_readv_writev fs/read_write.c:714 [inline]
 do_loop_readv_writev fs/read_write.c:701 [inline]
 do_iter_read+0x4a4/0x660 fs/read_write.c:935
 vfs_readv+0xf0/0x160 fs/read_write.c:997
 kernel_readv fs/splice.c:359 [inline]
 default_file_splice_read+0x475/0x890 fs/splice.c:414
 do_splice_to+0x127/0x180 fs/splice.c:877
 splice_direct_to_actor+0x2d2/0x970 fs/splice.c:954
 do_splice_direct+0x1da/0x2a0 fs/splice.c:1063
 do_sendfile+0x597/0xd00 fs/read_write.c:1464
 __do_sys_sendfile64 fs/read_write.c:1525 [inline]
 __se_sys_sendfile64 fs/read_write.c:1511 [inline]
 __x64_sys_sendfile64+0x1dd/0x220 fs/read_write.c:1511
 do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459279
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:00007fe6dae36c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000459279
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000004
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 000000010a000002 R11: 0000000000000246 R12: 00007fe6dae376d4
R13: 00000000004c65f3 R14: 00000000004db2a8 R15: 00000000ffffffff

Allocated by task 8852:
 save_stack+0x23/0x90 mm/kasan/common.c:71
 set_track mm/kasan/common.c:79 [inline]
 __kasan_kmalloc mm/kasan/common.c:489 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:462
 kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:497
 slab_post_alloc_hook mm/slab.h:444 [inline]
 slab_alloc mm/slab.c:3320 [inline]
 kmem_cache_alloc+0x11a/0x6f0 mm/slab.c:3482
 getname_flags fs/namei.c:138 [inline]
 getname_flags+0xd6/0x5b0 fs/namei.c:128
 getname fs/namei.c:209 [inline]
 user_path_create fs/namei.c:3692 [inline]
 do_mkdirat+0xa0/0x2a0 fs/namei.c:3830
 __do_sys_mkdirat fs/namei.c:3849 [inline]
 __se_sys_mkdirat fs/namei.c:3847 [inline]
 __x64_sys_mkdirat+0x76/0xb0 fs/namei.c:3847
 do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 8852:
 save_stack+0x23/0x90 mm/kasan/common.c:71
 set_track mm/kasan/common.c:79 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:451
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:459
 __cache_free mm/slab.c:3426 [inline]
 kmem_cache_free+0x86/0x320 mm/slab.c:3692
 putname+0xef/0x130 fs/namei.c:259
 filename_create+0x26f/0x4f0 fs/namei.c:3657
 user_path_create fs/namei.c:3692 [inline]
 do_mkdirat+0xb5/0x2a0 fs/namei.c:3830
 __do_sys_mkdirat fs/namei.c:3849 [inline]
 __se_sys_mkdirat fs/namei.c:3847 [inline]
 __x64_sys_mkdirat+0x76/0xb0 fs/namei.c:3847
 do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880997c6a40
 which belongs to the cache names_cache of size 4096
The buggy address is located 1436 bytes inside of
 4096-byte region [ffff8880997c6a40, ffff8880997c7a40)
The buggy address belongs to the page:
page:ffffea000265f180 refcount:1 mapcount:0 mapping:ffff8880aa594c40 index:0x0 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea00010b9e08 ffffea000251da88 ffff8880aa594c40
raw: 0000000000000000 ffff8880997c6a40 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880997c6e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880997c6f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880997c6f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                    ^
 ffff8880997c7000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880997c7080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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