Re: [syzbot] [mptcp?] KASAN: slab-use-after-free Read in __timer_delete_sync

[syzbot <syzbot+f3a31fb909db9b2a5c4d@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in remove_anno_list_by_saddr

============================================
WARNING: possible recursive locking detected
6.11.0-rc6-syzkaller-00019-g67784a74e258-dirty #0 Not tainted
--------------------------------------------
syz.1.16/6115 is trying to acquire lock:
ffff888028c116a0 (&msk->pm.lock){+.-.}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff888028c116a0 (&msk->pm.lock){+.-.}-{2:2}, at: mptcp_pm_del_add_timer net/mptcp/pm_netlink.c:338 [inline]
ffff888028c116a0 (&msk->pm.lock){+.-.}-{2:2}, at: remove_anno_list_by_saddr+0x24/0x190 net/mptcp/pm_netlink.c:1464

but task is already holding lock:
ffff888028c116a0 (&msk->pm.lock){+.-.}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff888028c116a0 (&msk->pm.lock){+.-.}-{2:2}, at: mptcp_pm_remove_addrs_and_subflows net/mptcp/pm_netlink.c:1682 [inline]
ffff888028c116a0 (&msk->pm.lock){+.-.}-{2:2}, at: mptcp_nl_remove_addrs_list net/mptcp/pm_netlink.c:1719 [inline]
ffff888028c116a0 (&msk->pm.lock){+.-.}-{2:2}, at: mptcp_pm_nl_flush_addrs_doit+0x509/0xd80 net/mptcp/pm_netlink.c:1760

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&msk->pm.lock);
  lock(&msk->pm.lock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

4 locks held by syz.1.16/6115:
 #0: ffffffff8fcf14b0 (cb_lock){++++}-{3:3}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
 #1: ffffffff8fcf1368 (genl_mutex){+.+.}-{3:3}, at: genl_lock net/netlink/genetlink.c:35 [inline]
 #1: ffffffff8fcf1368 (genl_mutex){+.+.}-{3:3}, at: genl_op_lock net/netlink/genetlink.c:60 [inline]
 #1: ffffffff8fcf1368 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg+0x121/0xec0 net/netlink/genetlink.c:1209
 #2: ffff888028c10e98 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1607 [inline]
 #2: ffff888028c10e98 (sk_lock-AF_INET6){+.+.}-{0:0}, at: mptcp_nl_remove_addrs_list net/mptcp/pm_netlink.c:1718 [inline]
 #2: ffff888028c10e98 (sk_lock-AF_INET6){+.+.}-{0:0}, at: mptcp_pm_nl_flush_addrs_doit+0x4d0/0xd80 net/mptcp/pm_netlink.c:1760
 #3: ffff888028c116a0 (&msk->pm.lock){+.-.}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
 #3: ffff888028c116a0 (&msk->pm.lock){+.-.}-{2:2}, at: mptcp_pm_remove_addrs_and_subflows net/mptcp/pm_netlink.c:1682 [inline]
 #3: ffff888028c116a0 (&msk->pm.lock){+.-.}-{2:2}, at: mptcp_nl_remove_addrs_list net/mptcp/pm_netlink.c:1719 [inline]
 #3: ffff888028c116a0 (&msk->pm.lock){+.-.}-{2:2}, at: mptcp_pm_nl_flush_addrs_doit+0x509/0xd80 net/mptcp/pm_netlink.c:1760

stack backtrace:
CPU: 0 UID: 0 PID: 6115 Comm: syz.1.16 Not tainted 6.11.0-rc6-syzkaller-00019-g67784a74e258-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:93 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119
 check_deadlock kernel/locking/lockdep.c:3061 [inline]
 validate_chain+0x15d3/0x5900 kernel/locking/lockdep.c:3855
 __lock_acquire+0x137a/0x2040 kernel/locking/lockdep.c:5142
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
 _raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178
 spin_lock_bh include/linux/spinlock.h:356 [inline]
 mptcp_pm_del_add_timer net/mptcp/pm_netlink.c:338 [inline]
 remove_anno_list_by_saddr+0x24/0x190 net/mptcp/pm_netlink.c:1464
 mptcp_pm_remove_addrs_and_subflows net/mptcp/pm_netlink.c:1689 [inline]
 mptcp_nl_remove_addrs_list net/mptcp/pm_netlink.c:1719 [inline]
 mptcp_pm_nl_flush_addrs_doit+0x689/0xd80 net/mptcp/pm_netlink.c:1760
 genl_family_rcv_msg_doit net/netlink/genetlink.c:1115 [inline]
 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
 genl_rcv_msg+0xb14/0xec0 net/netlink/genetlink.c:1210
 netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2550
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
 netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
 netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1357
 netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1901
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x221/0x270 net/socket.c:745
 ____sys_sendmsg+0x525/0x7d0 net/socket.c:2597
 ___sys_sendmsg net/socket.c:2651 [inline]
 __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2680
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb336579eb9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fb3372d5038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fb336715f80 RCX: 00007fb336579eb9
RDX: 0000000001000000 RSI: 0000000020000300 RDI: 0000000000000003
RBP: 00007fb3365e793e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fb336715f80 R15: 00007fb33683fa28
 </TASK>


Tested on:

commit:         67784a74 Merge tag 'ata-6.11-rc7' of git://git.kernel...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13ab2a8f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=660f6eb11f9c7dc5
dashboard link: https://syzkaller.appspot.com/bug?extid=f3a31fb909db9b2a5c4d
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1377f28f980000