syzbot

audit: type=1400 audit(1569730513.660:36): avc:  denied  { map } for  pid=7539 comm="syz-executor220" path="/root/syz-executor220385374" dev="sda1" ino=16483 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
IPVS: ftp: loaded support on port[0] = 21
==================================================================
BUG: KASAN: use-after-free in task_pid_ptr kernel/pid.c:274 [inline]
BUG: KASAN: use-after-free in __change_pid+0x253/0x2f0 kernel/pid.c:289
Read of size 8 at addr ffff888099b46e00 by task syz-executor220/7539

CPU: 1 PID: 7539 Comm: syz-executor220 Not tainted 4.19.75 #0
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+0x7c/0x20d mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report mm/kasan/report.c:412 [inline]
 kasan_report.cold+0x8c/0x2ba mm/kasan/report.c:396
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 task_pid_ptr kernel/pid.c:274 [inline]
 __change_pid+0x253/0x2f0 kernel/pid.c:289
 detach_pid+0x20/0x30 kernel/pid.c:307
 __unhash_process kernel/exit.c:78 [inline]
 __exit_signal kernel/exit.c:156 [inline]
 release_task+0xd65/0x1630 kernel/exit.c:201
 wait_task_zombie kernel/exit.c:1164 [inline]
 wait_consider_task+0x2c95/0x3910 kernel/exit.c:1391
 do_wait_thread kernel/exit.c:1454 [inline]
 do_wait+0x439/0x9d0 kernel/exit.c:1525
 kernel_wait4+0x171/0x290 kernel/exit.c:1668
 __do_sys_wait4+0x147/0x160 kernel/exit.c:1680
 __se_sys_wait4 kernel/exit.c:1676 [inline]
 __x64_sys_wait4+0x97/0xf0 kernel/exit.c:1676
 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x40113a
Code: c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 8b 05 9e 15 2d 00 85 c0 75 36 45 31 d2 48 63 d2 48 63 ff b8 3d 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 06 c3 0f 1f 44 00 00 48 c7 c2 d0 ff ff ff f7
RSP: 002b:00007ffea1edd4c8 EFLAGS: 00000246 ORIG_RAX: 000000000000003d
RAX: ffffffffffffffda RBX: 0000000000001d74 RCX: 000000000040113a
RDX: 0000000040000000 RSI: 00007ffea1edd4d4 RDI: ffffffffffffffff
RBP: 00000000006cb018 R08: 0000000000000000 R09: 0000555555a7e880
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004020f0
R13: 0000000000402180 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 7539:
 save_stack+0x45/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc mm/kasan/kasan.c:553 [inline]
 kasan_kmalloc+0xce/0xf0 mm/kasan/kasan.c:531
 kasan_slab_alloc+0xf/0x20 mm/kasan/kasan.c:490
 kmem_cache_alloc_node+0x144/0x710 mm/slab.c:3649
 alloc_task_struct_node kernel/fork.c:157 [inline]
 dup_task_struct kernel/fork.c:802 [inline]
 copy_process.part.0+0x1ce0/0x7a30 kernel/fork.c:1732
 copy_process kernel/fork.c:1689 [inline]
 _do_fork+0x257/0xfd0 kernel/fork.c:2202
 __do_sys_clone kernel/fork.c:2309 [inline]
 __se_sys_clone kernel/fork.c:2303 [inline]
 __x64_sys_clone+0xbf/0x150 kernel/fork.c:2303
 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 0:
 save_stack+0x45/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3503 [inline]
 kmem_cache_free+0x86/0x260 mm/slab.c:3765
 free_task_struct kernel/fork.c:162 [inline]
 free_task+0xdd/0x120 kernel/fork.c:416
 __put_task_struct+0x20f/0x4c0 kernel/fork.c:689
 put_task_struct include/linux/sched/task.h:96 [inline]
 finish_task_switch+0x52b/0x780 kernel/sched/core.c:2710
 context_switch kernel/sched/core.c:2829 [inline]
 __schedule+0x86e/0x1dc0 kernel/sched/core.c:3474
 schedule_idle+0x58/0x80 kernel/sched/core.c:3545
 do_idle+0x192/0x560 kernel/sched/idle.c:286
 cpu_startup_entry+0xc8/0xe0 kernel/sched/idle.c:368
 rest_init+0x219/0x222 init/main.c:442
 start_kernel+0x88c/0x8c5 init/main.c:738
 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:472
 x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:453
 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

The buggy address belongs to the object at ffff888099b46700
 which belongs to the cache task_struct of size 6080
The buggy address is located 1792 bytes inside of
 6080-byte region [ffff888099b46700, ffff888099b47ec0)
The buggy address belongs to the page:
page:ffffea000266d180 count:1 mapcount:0 mapping:ffff88812c26d800 index:0x0 compound_mapcount: 0
flags: 0x1fffc0000008100(slab|head)
raw: 01fffc0000008100 ffffea0002120908 ffffea000216d808 ffff88812c26d800
raw: 0000000000000000 ffff888099b46700 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888099b46d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888099b46d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888099b46e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888099b46e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888099b46f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================