Re: KASAN: use-after-free Read in rxrpc_put_peer

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer still triggered  
crash:
KASAN: use-after-free Read in rxrpc_release_call

==================================================================
BUG: KASAN: use-after-free in rxrpc_release_call+0x973/0xaa0  
net/rxrpc/call_object.c:498
Read of size 8 at addr ffff88808888b910 by task syz-executor.5/9000

CPU: 1 PID: 9000 Comm: syz-executor.5 Not tainted 5.3.0+ #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.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
 __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
 kasan_report+0x12/0x20 mm/kasan/common.c:634
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
 rxrpc_release_call+0x973/0xaa0 net/rxrpc/call_object.c:498
 rxrpc_release_calls_on_socket+0x6e7/0x1320 net/rxrpc/call_object.c:528
 rxrpc_release_sock net/rxrpc/af_rxrpc.c:897 [inline]
 rxrpc_release+0x2a6/0x550 net/rxrpc/af_rxrpc.c:927
 __sock_release+0xce/0x280 net/socket.c:590
 sock_close+0x1e/0x30 net/socket.c:1268
 __fput+0x2ff/0x890 fs/file_table.c:280
 ____fput+0x16/0x20 fs/file_table.c:313
 task_work_run+0x145/0x1c0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x316/0x380 arch/x86/entry/common.c:163
 prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
 do_syscall_64+0x65f/0x760 arch/x86/entry/common.c:300
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459a29
Code: fd 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 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f6e3d494c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000459a29
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f6e3d4956d4
R13: 00000000004f93d2 R14: 00000000004d1e00 R15: 00000000ffffffff

Allocated by task 9000:
 save_stack+0x23/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 __kasan_kmalloc mm/kasan/common.c:510 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:483
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:524
 kmem_cache_alloc_trace+0x158/0x790 mm/slab.c:3550
 kmalloc include/linux/slab.h:552 [inline]
 kzalloc include/linux/slab.h:686 [inline]
 rxrpc_alloc_connection+0x86/0x5f0 net/rxrpc/conn_object.c:41
 rxrpc_alloc_client_connection net/rxrpc/conn_client.c:176 [inline]
 rxrpc_get_client_conn net/rxrpc/conn_client.c:340 [inline]
 rxrpc_connect_call+0x648/0x4c30 net/rxrpc/conn_client.c:698
 rxrpc_new_client_call+0x9c0/0x1ad0 net/rxrpc/call_object.c:290
 rxrpc_new_client_call_for_sendmsg net/rxrpc/sendmsg.c:595 [inline]
 rxrpc_do_sendmsg+0xffa/0x1d5f net/rxrpc/sendmsg.c:652
 rxrpc_sendmsg+0x4d6/0x5f0 net/rxrpc/af_rxrpc.c:585
 sock_sendmsg_nosec net/socket.c:637 [inline]
 sock_sendmsg+0xd7/0x130 net/socket.c:657
 ___sys_sendmsg+0x3e2/0x920 net/socket.c:2311
 __sys_sendmmsg+0x1bf/0x4d0 net/socket.c:2413
 __do_sys_sendmmsg net/socket.c:2442 [inline]
 __se_sys_sendmmsg net/socket.c:2439 [inline]
 __x64_sys_sendmmsg+0x9d/0x100 net/socket.c:2439
 do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 16:
 save_stack+0x23/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 kasan_set_free_info mm/kasan/common.c:332 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:471
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:480
 __cache_free mm/slab.c:3425 [inline]
 kfree+0x10a/0x2c0 mm/slab.c:3756
 rxrpc_destroy_connection+0x1f2/0x2d0 net/rxrpc/conn_object.c:373
 __rcu_reclaim kernel/rcu/rcu.h:222 [inline]
 rcu_do_batch kernel/rcu/tree.c:2157 [inline]
 rcu_core+0x581/0x1560 kernel/rcu/tree.c:2377
 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2386
 __do_softirq+0x262/0x98c kernel/softirq.c:292

The buggy address belongs to the object at ffff88808888b6c0
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 592 bytes inside of
 1024-byte region [ffff88808888b6c0, ffff88808888bac0)
The buggy address belongs to the page:
page:ffffea0002222280 refcount:1 mapcount:0 mapping:ffff8880aa400c40  
index:0xffff88808888bb40 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea000220ae88 ffffea0002809108 ffff8880aa400c40
raw: ffff88808888bb40 ffff88808888a040 0000000100000002 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808888b800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808888b880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88808888b900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff88808888b980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808888ba00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Tested on:

commit:         cc9604d4 rxrpc: rxrpc_peer needs to hold a ref on the rxrp..
git tree:        
git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git
console output: https://syzkaller.appspot.com/x/log.txt?x=126c3899600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6ffbfa7e4a36190f
dashboard link: https://syzkaller.appspot.com/bug?extid=b9be979c55f2bea8ed30
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)