syzbot

audit: type=1400 audit(1569890881.338:36): avc:  denied  { map } for  pid=7478 comm="syz-executor361" path="/root/syz-executor361844896" dev="sda1" ino=16484 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
==================================================================
BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:193 [inline]
BUG: KASAN: use-after-free in wait_consider_task+0x1b51/0x3910 kernel/exit.c:1345
Read of size 4 at addr ffff88809c2a4a6c by task syz-executor361/7478

CPU: 0 PID: 7478 Comm: syz-executor361 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_load4_noabort+0x14/0x20 mm/kasan/report.c:432
 __read_once_size include/linux/compiler.h:193 [inline]
 wait_consider_task+0x1b51/0x3910 kernel/exit.c:1345
 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: 0033:0x40110a
Code: c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 8b 05 ce 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:00007ffebad6cd68 EFLAGS: 00000246 ORIG_RAX: 000000000000003d
RAX: ffffffffffffffda RBX: 0000000000001d37 RCX: 000000000040110a
RDX: 0000000040000001 RSI: 00007ffebad6cd74 RDI: ffffffffffffffff
RBP: 000000000000ebd6 R08: 0000000000000000 R09: 0000555555a21880
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004020c0
R13: 0000000000402150 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 7478:
 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 7480:
 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
 preempt_schedule_irq+0xb5/0x140 kernel/sched/core.c:3701
 retint_kernel+0x1b/0x2d
 stack_not_used include/linux/sched/task_stack.h:93 [inline]
 check_stack_usage kernel/exit.c:757 [inline]
 do_exit+0x1f06/0x2fa0 kernel/exit.c:925
 kthread+0x2c3/0x420 kernel/kthread.c:248
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

The buggy address belongs to the object at ffff88809c2a4600
 which belongs to the cache task_struct of size 6080
The buggy address is located 1132 bytes inside of
 6080-byte region [ffff88809c2a4600, ffff88809c2a5dc0)
The buggy address belongs to the page:
page:ffffea000270a900 count:1 mapcount:0 mapping:ffff88812c26d800 index:0x0 compound_mapcount: 0
flags: 0x1fffc0000008100(slab|head)
raw: 01fffc0000008100 ffffea000244a988 ffffea000248fa88 ffff88812c26d800
raw: 0000000000000000 ffff88809c2a4600 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88809c2a4900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88809c2a4980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88809c2a4a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                          ^
 ffff88809c2a4a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88809c2a4b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================