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SubjectKASAN: use-after-free Write in rxrpc_put_bundle

syzbot found the following issue on:

HEAD commit: ed6d9b02 ionic: fix up debugfs after queue swap
git tree: net-next
console output:
kernel config:
dashboard link:
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro:
C reproducer:

The issue was bisected to:

commit 245500d853e9f20036cec7df4f6984ece4c6bf26
Author: David Howells <>
Date: Wed Jul 1 10:15:32 2020 +0000

rxrpc: Rewrite the client connection manager

bisection log:
final oops:
console output:

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Fixes: 245500d853e9 ("rxrpc: Rewrite the client connection manager")

BUG: KASAN: use-after-free in instrument_atomic_write include/linux/instrumented.h:71 [inline]
BUG: KASAN: use-after-free in atomic_dec_return include/asm-generic/atomic-instrumented.h:340 [inline]
BUG: KASAN: use-after-free in rxrpc_put_bundle+0x1d/0x80 net/rxrpc/conn_client.c:141
Write of size 4 at addr ffff8880a8669220 by task ksoftirqd/0/9

CPU: 0 PID: 9 Comm: ksoftirqd/0 Not tainted 5.9.0-rc3-syzkaller #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+0x198/0x1fd lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
check_memory_region_inline mm/kasan/generic.c:186 [inline]
check_memory_region+0x13d/0x180 mm/kasan/generic.c:192
instrument_atomic_write include/linux/instrumented.h:71 [inline]
atomic_dec_return include/asm-generic/atomic-instrumented.h:340 [inline]
rxrpc_put_bundle+0x1d/0x80 net/rxrpc/conn_client.c:141
rxrpc_destroy_connection+0x150/0x2f0 net/rxrpc/conn_object.c:367
rcu_do_batch kernel/rcu/tree.c:2428 [inline]
rcu_core+0x5ca/0x1130 kernel/rcu/tree.c:2656
__do_softirq+0x1f7/0xa91 kernel/softirq.c:298
run_ksoftirqd kernel/softirq.c:652 [inline]
run_ksoftirqd+0xcf/0x170 kernel/softirq.c:644
smpboot_thread_fn+0x655/0x9e0 kernel/smpboot.c:165
kthread+0x3b5/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Allocated by task 6875:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
kmem_cache_alloc_trace+0x174/0x2c0 mm/slab.c:3550
kmalloc include/linux/slab.h:554 [inline]
kzalloc include/linux/slab.h:666 [inline]
rxrpc_alloc_bundle+0x7e/0x290 net/rxrpc/conn_client.c:121
rxrpc_look_up_bundle net/rxrpc/conn_client.c:275 [inline]
rxrpc_prep_call net/rxrpc/conn_client.c:374 [inline]
rxrpc_connect_call+0x85c/0x1580 net/rxrpc/conn_client.c:710
rxrpc_new_client_call+0x961/0x1020 net/rxrpc/call_object.c:331
rxrpc_new_client_call_for_sendmsg net/rxrpc/sendmsg.c:622 [inline]
rxrpc_do_sendmsg+0xf14/0x136d net/rxrpc/sendmsg.c:679
rxrpc_sendmsg+0x420/0x630 net/rxrpc/af_rxrpc.c:560
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:671
____sys_sendmsg+0x331/0x810 net/socket.c:2353
___sys_sendmsg+0xf3/0x170 net/socket.c:2407
__sys_sendmmsg+0x195/0x480 net/socket.c:2497
__do_sys_sendmmsg net/socket.c:2526 [inline]
__se_sys_sendmmsg net/socket.c:2523 [inline]
__x64_sys_sendmmsg+0x99/0x100 net/socket.c:2523
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46

Freed by task 2642:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_set_track+0x1c/0x30 mm/kasan/common.c:56
kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355
__kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422
__cache_free mm/slab.c:3418 [inline]
kfree+0x10e/0x2b0 mm/slab.c:3756
rxrpc_put_bundle net/rxrpc/conn_client.c:146 [inline]
rxrpc_put_bundle+0x6b/0x80 net/rxrpc/conn_client.c:138
rxrpc_unbundle_conn+0x1f8/0x3d0 net/rxrpc/conn_client.c:935
rxrpc_clean_up_local_conns+0x38d/0x587 net/rxrpc/conn_client.c:1114
rxrpc_local_destroyer net/rxrpc/local_object.c:399 [inline]
rxrpc_local_processor+0x38d/0x5e0 net/rxrpc/local_object.c:433
process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
kthread+0x3b5/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

The buggy address belongs to the object at ffff8880a8669200
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 32 bytes inside of
192-byte region [ffff8880a8669200, ffff8880a86692c0)
The buggy address belongs to the page:
page:000000007bfb6cde refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8880a8669d00 pfn:0xa8669
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002a42f88 ffffea00027d8f08 ffff8880aa040000
raw: ffff8880a8669d00 ffff8880a8669000 000000010000000d 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a8669100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a8669180: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff8880a8669200: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a8669280: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff8880a8669300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

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