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SubjectKASAN: use-after-free Read in oom_kill_process
From
Hello,

syzbot found the following crash on:

HEAD commit: 47bfa6d9dc8c Merge tag 'selinux-pr-20190115' of git://git...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=123af46b400000
kernel config: https://syzkaller.appspot.com/x/.config?x=8a4dffabfb4e36f9
dashboard link: https://syzkaller.appspot.com/bug?extid=7fbbfa368521945f0e3d
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+7fbbfa368521945f0e3d@syzkaller.appspotmail.com

kmem: usage 0kB, limit 9007199254740988kB, failcnt 0
Memory cgroup stats for /syz1: cache:28KB rss:274692KB rss_huge:190464KB
shmem:64KB mapped_file:0KB dirty:0KB writeback:0KB swap:0KB
inactive_anon:222780KB active_anon:4152KB inactive_file:0KB active_file:0KB
unevictable:47872KB
oom-kill:constraint=CONSTRAINT_NONE,nodemask=(null),cpuset=syz1,mems_allowed=0-1,oom_memcg=/syz1,task_memcg=/syz1,task=syz-executor1,pid=15858,uid=0
Memory cgroup out of memory: Kill process 15858 (syz-executor1) score 1148
or sacrifice child
==================================================================
BUG: KASAN: use-after-free in oom_kill_process.cold+0x484/0x9d4
mm/oom_kill.c:978
Read of size 8 at addr ffff8880595f6c40 by task syz-executor1/15817

CPU: 1 PID: 15817 Comm: syz-executor1 Not tainted 5.0.0-rc2+ #29
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+0x1db/0x2d0 lib/dump_stack.c:113
print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
__asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
oom_kill_process.cold+0x484/0x9d4 mm/oom_kill.c:978
out_of_memory+0x885/0x1420 mm/oom_kill.c:1133
mem_cgroup_out_of_memory+0x160/0x210 mm/memcontrol.c:1393
mem_cgroup_oom mm/memcontrol.c:1721 [inline]
try_charge+0xd44/0x19b0 mm/memcontrol.c:2283
memcg_kmem_charge_memcg+0x7c/0x130 mm/memcontrol.c:2591
memcg_kmem_charge+0x13b/0x340 mm/memcontrol.c:2624
__alloc_pages_nodemask+0x7b8/0xdc0 mm/page_alloc.c:4559
__alloc_pages include/linux/gfp.h:473 [inline]
__alloc_pages_node include/linux/gfp.h:486 [inline]
alloc_pages_node include/linux/gfp.h:500 [inline]
alloc_thread_stack_node kernel/fork.c:246 [inline]
dup_task_struct kernel/fork.c:849 [inline]
copy_process+0x847/0x8710 kernel/fork.c:1753
_do_fork+0x1a9/0x1170 kernel/fork.c:2227
__do_sys_clone kernel/fork.c:2334 [inline]
__se_sys_clone kernel/fork.c:2328 [inline]
__x64_sys_clone+0xbf/0x150 kernel/fork.c:2328
do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457ec9
Code: 6d 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 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f36f091cc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000457ec9
RDX: 9999999999999999 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 000000000073bf00 R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f36f091d6d4
R13: 00000000004be2a0 R14: 00000000004ce760 R15: 00000000ffffffff

Allocated by task 15809:
save_stack+0x45/0xd0 mm/kasan/common.c:73
set_track mm/kasan/common.c:85 [inline]
__kasan_kmalloc mm/kasan/common.c:496 [inline]
__kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:469
kasan_kmalloc mm/kasan/common.c:504 [inline]
kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:411
kmem_cache_alloc_node+0x144/0x710 mm/slab.c:3633
alloc_task_struct_node kernel/fork.c:158 [inline]
dup_task_struct kernel/fork.c:845 [inline]
copy_process+0x405b/0x8710 kernel/fork.c:1753
_do_fork+0x1a9/0x1170 kernel/fork.c:2227
__do_sys_clone kernel/fork.c:2334 [inline]
__se_sys_clone kernel/fork.c:2328 [inline]
__x64_sys_clone+0xbf/0x150 kernel/fork.c:2328
do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 15817:
save_stack+0x45/0xd0 mm/kasan/common.c:73
set_track mm/kasan/common.c:85 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/common.c:458
kasan_slab_free+0xe/0x10 mm/kasan/common.c:466
__cache_free mm/slab.c:3487 [inline]
kmem_cache_free+0x86/0x260 mm/slab.c:3749
free_task_struct kernel/fork.c:163 [inline]
free_task+0x170/0x1f0 kernel/fork.c:458
__put_task_struct+0x2e0/0x630 kernel/fork.c:731
put_task_struct+0x4b/0x60 include/linux/sched/task.h:98
oom_kill_process.cold+0x93a/0x9d4 mm/oom_kill.c:990
out_of_memory+0x885/0x1420 mm/oom_kill.c:1133
mem_cgroup_out_of_memory+0x160/0x210 mm/memcontrol.c:1393
mem_cgroup_oom mm/memcontrol.c:1721 [inline]
try_charge+0xd44/0x19b0 mm/memcontrol.c:2283
memcg_kmem_charge_memcg+0x7c/0x130 mm/memcontrol.c:2591
memcg_kmem_charge+0x13b/0x340 mm/memcontrol.c:2624
__alloc_pages_nodemask+0x7b8/0xdc0 mm/page_alloc.c:4559
__alloc_pages include/linux/gfp.h:473 [inline]
__alloc_pages_node include/linux/gfp.h:486 [inline]
alloc_pages_node include/linux/gfp.h:500 [inline]
alloc_thread_stack_node kernel/fork.c:246 [inline]
dup_task_struct kernel/fork.c:849 [inline]
copy_process+0x847/0x8710 kernel/fork.c:1753
_do_fork+0x1a9/0x1170 kernel/fork.c:2227
__do_sys_clone kernel/fork.c:2334 [inline]
__se_sys_clone kernel/fork.c:2328 [inline]
__x64_sys_clone+0xbf/0x150 kernel/fork.c:2328
do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880595f6540
which belongs to the cache task_struct(33:syz1) of size 6080
The buggy address is located 1792 bytes inside of
6080-byte region [ffff8880595f6540, ffff8880595f7d00)
The buggy address belongs to the page:
page:ffffea0001657d80 count:1 mapcount:0 mapping:ffff888091f65840 index:0x0
compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea00028b3288 ffffea0002612788 ffff888091f65840
raw: 0000000000000000 ffff8880595f6540 0000000100000001 ffff888057fe2b00
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff888057fe2b00

Memory state around the buggy address:
ffff8880595f6b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880595f6b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8880595f6c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880595f6c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880595f6d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
protocol 88fb is buggy, dev hsr_slave_0
protocol 88fb is buggy, dev hsr_slave_1
protocol 88fb is buggy, dev hsr_slave_0
protocol 88fb is buggy, dev hsr_slave_1


---
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 syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
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syzbot.

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