KASAN: use-after-free Read in __change_pid

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: d573e8a7 Linux 4.19.75
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16074d09600000
kernel config: https://syzkaller.appspot.com/x/.config?x=50b385e67c7b7cdf
dashboard link: https://syzkaller.appspot.com/bug?extid=2d3a8e0404649fea569b
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1303038d600000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16950991600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2d3a8e...@syzkaller.appspotmail.com

audit: type=1400 audit(1569077913.142:36): avc: denied { map } for
pid=7418 comm="syz-executor317" path="/root/syz-executor317646007"
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 ffff8880a17b8c80 by task syz-executor317/7418

CPU: 1 PID: 7418 Comm: syz-executor317 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:00007ffded8f4c08 EFLAGS: 00000246 ORIG_RAX: 000000000000003d
RAX: ffffffffffffffda RBX: 0000000000001cfb RCX: 000000000040113a
RDX: 0000000040000000 RSI: 00007ffded8f4c14 RDI: ffffffffffffffff
RBP: 00000000006cb018 R08: 0000000000000000 R09: 00005555570dd880
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004020f0
R13: 0000000000402180 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 7418:
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 ffff8880a17b8580
which belongs to the cache task_struct of size 6080
The buggy address is located 1792 bytes inside of
6080-byte region [ffff8880a17b8580, ffff8880a17b9d40)
The buggy address belongs to the page:
page:ffffea000285ee00 count:1 mapcount:0 mapping:ffff88812c26d800 index:0x0
compound_mapcount: 0
flags: 0x1fffc0000008100(slab|head)
raw: 01fffc0000008100 ffffea00020d7e88 ffffea00026fac88 ffff88812c26d800
raw: 0000000000000000 ffff8880a17b8580 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a17b8b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a17b8c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8880a17b8c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880a17b8d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a17b8d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

[syzbot]

syzbot suspects this bug was fixed by commit:

commit 4eb92a1148342af1d6f82018d20cd862e1d3ab7e
Author: Leon Romanovsky <leo...@mellanox.com>
Date: Thu Oct 11 19:10:10 2018 +0000

RDMA/restrack: Protect from reentry to resource return path

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10e9e59ce00000
start commit: d573e8a7 Linux 4.19.75
git tree: linux-4.19.y

kernel config: https://syzkaller.appspot.com/x/.config?x=50b385e67c7b7cdf
dashboard link: https://syzkaller.appspot.com/bug?extid=2d3a8e0404649fea569b

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1303038d600000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16950991600000

If the result looks correct, please mark the bug fixed by replying with:

#syz fix: RDMA/restrack: Protect from reentry to resource return path

For information about bisection process see: https://goo.gl/tpsmEJ#bisection