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SubjectKASAN: use-after-free Read in rds_cong_queue_updates (2)
From
Hello,

syzbot found the following crash on:

HEAD commit: fcf4793e278e tls: check RCV_SHUTDOWN in tls_wait_data
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=1738cb2c400000
kernel config: https://syzkaller.appspot.com/x/.config?x=c0bdc4175608181c
dashboard link: https://syzkaller.appspot.com/bug?extid=470ae97a39f16146af45
compiler: gcc (GCC) 8.0.1 20180413 (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+470ae97a39f16146af45@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in atomic_read
include/asm-generic/atomic-instrumented.h:21 [inline]
BUG: KASAN: use-after-free in refcount_read include/linux/refcount.h:42
[inline]
BUG: KASAN: use-after-free in check_net include/net/net_namespace.h:237
[inline]
BUG: KASAN: use-after-free in rds_destroy_pending net/rds/rds.h:902 [inline]
BUG: KASAN: use-after-free in rds_cong_queue_updates+0x25d/0x5b0
net/rds/cong.c:226
Read of size 4 at addr ffff88019f180144 by task kworker/u4:1/23

CPU: 1 PID: 23 Comm: kworker/u4:1 Not tainted 4.18.0-rc5+ #18
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: krdsd rds_send_worker
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
print_address_description+0x6c/0x20b mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
check_memory_region_inline mm/kasan/kasan.c:260 [inline]
check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
kasan_check_read+0x11/0x20 mm/kasan/kasan.c:272
atomic_read include/asm-generic/atomic-instrumented.h:21 [inline]
refcount_read include/linux/refcount.h:42 [inline]
check_net include/net/net_namespace.h:237 [inline]
rds_destroy_pending net/rds/rds.h:902 [inline]
rds_cong_queue_updates+0x25d/0x5b0 net/rds/cong.c:226
rds_recv_rcvbuf_delta.part.3+0x332/0x3e0 net/rds/recv.c:123
rds_recv_rcvbuf_delta net/rds/recv.c:382 [inline]
rds_recv_incoming+0x85a/0x1320 net/rds/recv.c:382
rds_loop_xmit+0x16a/0x340 net/rds/loop.c:95
rds_send_xmit+0x1343/0x29c0 net/rds/send.c:355
rds_send_worker+0x153/0x300 net/rds/threads.c:199
process_one_work+0xc73/0x1ba0 kernel/workqueue.c:2153
worker_thread+0x189/0x13c0 kernel/workqueue.c:2296
kthread+0x345/0x410 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

Allocated by task 4564:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
kmem_cache_alloc+0x12e/0x760 mm/slab.c:3554
kmem_cache_zalloc include/linux/slab.h:697 [inline]
net_alloc net/core/net_namespace.c:383 [inline]
copy_net_ns+0x15b/0x4d0 net/core/net_namespace.c:423
create_new_namespaces+0x6ad/0x900 kernel/nsproxy.c:107
unshare_nsproxy_namespaces+0xc3/0x1f0 kernel/nsproxy.c:206
ksys_unshare+0x723/0xfb0 kernel/fork.c:2419
__do_sys_unshare kernel/fork.c:2487 [inline]
__se_sys_unshare kernel/fork.c:2485 [inline]
__x64_sys_unshare+0x31/0x40 kernel/fork.c:2485
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 23:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kmem_cache_free+0x86/0x2d0 mm/slab.c:3756
net_free net/core/net_namespace.c:399 [inline]
net_drop_ns.part.14+0x129/0x150 net/core/net_namespace.c:406
net_drop_ns net/core/net_namespace.c:405 [inline]
cleanup_net+0x6bb/0xb50 net/core/net_namespace.c:541
process_one_work+0xc73/0x1ba0 kernel/workqueue.c:2153
worker_thread+0x189/0x13c0 kernel/workqueue.c:2296
kthread+0x345/0x410 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

The buggy address belongs to the object at ffff88019f180140
which belongs to the cache net_namespace of size 8704
The buggy address is located 4 bytes inside of
8704-byte region [ffff88019f180140, ffff88019f182340)
The buggy address belongs to the page:
page:ffffea00067c6000 count:1 mapcount:0 mapping:ffff8801d9be9e40 index:0x0
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffffea00067d5a08 ffffea00067b3a08 ffff8801d9be9e40
raw: 0000000000000000 ffff88019f180140 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88019f180000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88019f180080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff88019f180100: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
^
ffff88019f180180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88019f180200: 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 syzkaller@googlegroups.com.

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

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