[syzbot] KASAN: use-after-free Write in dec_ucount

From: syzbot
Date: Mon Jul 05 2021 - 05:20:31 EST

Next message: kernel test robot: "[rcu:linus-fixup.2021.07.04a] BUILD SUCCESS 948d10a5f2d2f157b1f50cc19b1a7ff4bda491b9"
Previous message: Juergen Gross: "Re: [PATCH] xen/events: reset active flag for lateeoi events later"
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Hello,

syzbot found the following issue on:

HEAD commit: 3dbdb38e Merge branch 'for-5.14' of git://git.kernel.org/p..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14c692e4300000
kernel config: https://syzkaller.appspot.com/x/.config?x=a1fcf15a09815757
dashboard link: https://syzkaller.appspot.com/bug?extid=ed34370dbda6d44c06b2

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ed34370dbda6d44c06b2@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in atomic64_dec_if_positive include/asm-generic/atomic-instrumented.h:1176 [inline]
BUG: KASAN: use-after-free in atomic_long_dec_if_positive include/asm-generic/atomic-long.h:515 [inline]
BUG: KASAN: use-after-free in dec_ucount+0x54/0x130 kernel/ucount.c:245
Write of size 8 at addr ffff888017d7d840 by task kworker/u4:4/24672

CPU: 0 PID: 24672 Comm: kworker/u4:4 Tainted: G W 5.13.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: netns cleanup_net
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:96
print_address_description.constprop.0.cold+0x6c/0x309 mm/kasan/report.c:233
__kasan_report mm/kasan/report.c:419 [inline]
kasan_report.cold+0x83/0xdf mm/kasan/report.c:436
check_region_inline mm/kasan/generic.c:183 [inline]
kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
atomic64_dec_if_positive include/asm-generic/atomic-instrumented.h:1176 [inline]
atomic_long_dec_if_positive include/asm-generic/atomic-long.h:515 [inline]
dec_ucount+0x54/0x130 kernel/ucount.c:245
dec_net_namespaces net/core/net_namespace.c:394 [inline]
cleanup_net+0x6f3/0xb10 net/core/net_namespace.c:611
process_one_work+0x98d/0x1630 kernel/workqueue.c:2276
worker_thread+0x658/0x11f0 kernel/workqueue.c:2422
kthread+0x3e5/0x4d0 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Allocated by task 8464:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:434 [inline]
____kasan_kmalloc mm/kasan/common.c:513 [inline]
____kasan_kmalloc mm/kasan/common.c:472 [inline]
__kasan_kmalloc+0x9b/0xd0 mm/kasan/common.c:522
kmalloc include/linux/slab.h:591 [inline]
kzalloc include/linux/slab.h:721 [inline]
alloc_ucounts+0x23d/0x5b0 kernel/ucount.c:169
set_cred_ucounts+0x171/0x3a0 kernel/cred.c:684
copy_creds+0x853/0xb20 kernel/cred.c:375
copy_process+0x1413/0x74c0 kernel/fork.c:1992
kernel_clone+0xe7/0xab0 kernel/fork.c:2509
__do_sys_clone+0xc8/0x110 kernel/fork.c:2626
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 13:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:360
____kasan_slab_free mm/kasan/common.c:366 [inline]
____kasan_slab_free mm/kasan/common.c:328 [inline]
__kasan_slab_free+0xfb/0x130 mm/kasan/common.c:374
kasan_slab_free include/linux/kasan.h:229 [inline]
slab_free_hook mm/slub.c:1639 [inline]
slab_free_freelist_hook+0xdf/0x240 mm/slub.c:1664
slab_free mm/slub.c:3224 [inline]
kfree+0xeb/0x670 mm/slub.c:4268
put_ucounts kernel/ucount.c:200 [inline]
put_ucounts+0x117/0x150 kernel/ucount.c:192
dec_pid_namespaces kernel/pid_namespace.c:67 [inline]
delayed_free_pidns+0x3f/0x120 kernel/pid_namespace.c:127
rcu_do_batch kernel/rcu/tree.c:2558 [inline]
rcu_core+0x7ab/0x1380 kernel/rcu/tree.c:2793
__do_softirq+0x29b/0x9bd kernel/softirq.c:558

Last potentially related work creation:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
kasan_record_aux_stack+0xe5/0x110 mm/kasan/generic.c:348
insert_work+0x48/0x370 kernel/workqueue.c:1332
__queue_work+0x5c1/0xed0 kernel/workqueue.c:1498
queue_work_on+0xee/0x110 kernel/workqueue.c:1525
queue_work include/linux/workqueue.h:507 [inline]
call_usermodehelper_exec+0x1f0/0x4c0 kernel/umh.c:435
kobject_uevent_env+0xf8f/0x1650 lib/kobject_uevent.c:618
kobject_synth_uevent+0x701/0x850 lib/kobject_uevent.c:208
uevent_store+0x42/0x90 drivers/base/bus.c:585
drv_attr_store+0x6d/0xa0 drivers/base/bus.c:77
sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:139
kernfs_fop_write_iter+0x342/0x500 fs/kernfs/file.c:296
call_write_iter include/linux/fs.h:2114 [inline]
new_sync_write+0x426/0x650 fs/read_write.c:518
vfs_write+0x796/0xa30 fs/read_write.c:605
ksys_write+0x12d/0x250 fs/read_write.c:658
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

Second to last potentially related work creation:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
kasan_record_aux_stack+0xe5/0x110 mm/kasan/generic.c:348
insert_work+0x48/0x370 kernel/workqueue.c:1332
__queue_work+0x5c1/0xed0 kernel/workqueue.c:1498
queue_work_on+0xee/0x110 kernel/workqueue.c:1525
queue_work include/linux/workqueue.h:507 [inline]
call_usermodehelper_exec+0x1f0/0x4c0 kernel/umh.c:435
kobject_uevent_env+0xf8f/0x1650 lib/kobject_uevent.c:618
kernel_add_sysfs_param kernel/params.c:798 [inline]
param_sysfs_builtin kernel/params.c:833 [inline]
param_sysfs_init+0x3bf/0x498 kernel/params.c:952
do_one_initcall+0x103/0x650 init/main.c:1246
do_initcall_level init/main.c:1319 [inline]
do_initcalls init/main.c:1335 [inline]
do_basic_setup init/main.c:1355 [inline]
kernel_init_freeable+0x6b8/0x741 init/main.c:1557
kernel_init+0x1a/0x1d0 init/main.c:1449
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

The buggy address belongs to the object at ffff888017d7d800
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 64 bytes inside of
192-byte region [ffff888017d7d800, ffff888017d7d8c0)
The buggy address belongs to the page:
page:ffffea00005f5f40 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x17d7d
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 0000000000000000 0000000300000001 ffff888011041a00
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 1, ts 3073366427, free_ts 2934084203
prep_new_page mm/page_alloc.c:2445 [inline]
get_page_from_freelist+0xa72/0x2f80 mm/page_alloc.c:4178
__alloc_pages+0x1b2/0x500 mm/page_alloc.c:5386
alloc_page_interleave+0x1e/0x200 mm/mempolicy.c:2147
alloc_pages+0x238/0x2a0 mm/mempolicy.c:2270
alloc_slab_page mm/slub.c:1702 [inline]
allocate_slab+0x32b/0x4c0 mm/slub.c:1842
new_slab mm/slub.c:1905 [inline]
new_slab_objects mm/slub.c:2651 [inline]
___slab_alloc+0x4ba/0x820 mm/slub.c:2814
__slab_alloc.constprop.0+0xa7/0xf0 mm/slub.c:2854
slab_alloc_node mm/slub.c:2936 [inline]
slab_alloc mm/slub.c:2978 [inline]
kmem_cache_alloc_trace+0x325/0x3c0 mm/slub.c:2995
kmalloc include/linux/slab.h:591 [inline]
kzalloc include/linux/slab.h:721 [inline]
call_usermodehelper_setup+0x97/0x340 kernel/umh.c:365
kobject_uevent_env+0xf73/0x1650 lib/kobject_uevent.c:614
kernel_add_sysfs_param kernel/params.c:798 [inline]
param_sysfs_builtin kernel/params.c:833 [inline]
param_sysfs_init+0x3bf/0x498 kernel/params.c:952
do_one_initcall+0x103/0x650 init/main.c:1246
do_initcall_level init/main.c:1319 [inline]
do_initcalls init/main.c:1335 [inline]
do_basic_setup init/main.c:1355 [inline]
kernel_init_freeable+0x6b8/0x741 init/main.c:1557
kernel_init+0x1a/0x1d0 init/main.c:1449
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1355 [inline]
free_pcp_prepare+0x2c5/0x780 mm/page_alloc.c:1406
free_unref_page_prepare mm/page_alloc.c:3341 [inline]
free_unref_page_list+0x1a1/0x1050 mm/page_alloc.c:3457
release_pages+0x856/0x20a0 mm/swap.c:972
tlb_batch_pages_flush mm/mmu_gather.c:49 [inline]
tlb_flush_mmu_free mm/mmu_gather.c:242 [inline]
tlb_flush_mmu mm/mmu_gather.c:249 [inline]
tlb_finish_mmu+0x165/0x8c0 mm/mmu_gather.c:340
exit_mmap+0x1ea/0x620 mm/mmap.c:3204
__mmput+0x122/0x470 kernel/fork.c:1101
mmput+0x58/0x60 kernel/fork.c:1122
free_bprm+0x65/0x2e0 fs/exec.c:1482
kernel_execve+0x380/0x460 fs/exec.c:1979
call_usermodehelper_exec_async+0x2e3/0x580 kernel/umh.c:112
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Memory state around the buggy address:
ffff888017d7d700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888017d7d780: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
>ffff888017d7d800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888017d7d880: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff888017d7d900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

---
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Next message: kernel test robot: "[rcu:linus-fixup.2021.07.04a] BUILD SUCCESS 948d10a5f2d2f157b1f50cc19b1a7ff4bda491b9"
Previous message: Juergen Gross: "Re: [PATCH] xen/events: reset active flag for lateeoi events later"
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