mptcp: pm: fix UaF read in mptcp_pm_nl_rm_addr_or_subflow

Syzkaller reported this splat:

  ==================================================================
  BUG: KASAN: slab-use-after-free in mptcp_pm_nl_rm_addr_or_subflow+0xb44/0xcc0 net/mptcp/pm_netlink.c:881
  Read of size 4 at addr ffff8880569ac858 by task syz.1.2799/14662

  CPU: 0 UID: 0 PID: 14662 Comm: syz.1.2799 Not tainted 6.12.0-rc2-syzkaller-00307-g36c254515dc6 #0
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
  Call Trace:
   <TASK>
   __dump_stack lib/dump_stack.c:94 [inline]
   dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
   print_address_description mm/kasan/report.c:377 [inline]
   print_report+0xc3/0x620 mm/kasan/report.c:488
   kasan_report+0xd9/0x110 mm/kasan/report.c:601
   mptcp_pm_nl_rm_addr_or_subflow+0xb44/0xcc0 net/mptcp/pm_netlink.c:881
   mptcp_pm_nl_rm_subflow_received net/mptcp/pm_netlink.c:914 [inline]
   mptcp_nl_remove_id_zero_address+0x305/0x4a0 net/mptcp/pm_netlink.c:1572
   mptcp_pm_nl_del_addr_doit+0x5c9/0x770 net/mptcp/pm_netlink.c:1603
   genl_family_rcv_msg_doit+0x202/0x2f0 net/netlink/genetlink.c:1115
   genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
   genl_rcv_msg+0x565/0x800 net/netlink/genetlink.c:1210
   netlink_rcv_skb+0x165/0x410 net/netlink/af_netlink.c:2551
   genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
   netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
   netlink_unicast+0x53c/0x7f0 net/netlink/af_netlink.c:1357
   netlink_sendmsg+0x8b8/0xd70 net/netlink/af_netlink.c:1901
   sock_sendmsg_nosec net/socket.c:729 [inline]
   __sock_sendmsg net/socket.c:744 [inline]
   ____sys_sendmsg+0x9ae/0xb40 net/socket.c:2607
   ___sys_sendmsg+0x135/0x1e0 net/socket.c:2661
   __sys_sendmsg+0x117/0x1f0 net/socket.c:2690
   do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
   __do_fast_syscall_32+0x73/0x120 arch/x86/entry/common.c:386
   do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
   entry_SYSENTER_compat_after_hwframe+0x84/0x8e
  RIP: 0023:0xf7fe4579
  Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
  RSP: 002b:00000000f574556c EFLAGS: 00000296 ORIG_RAX: 0000000000000172
  RAX: ffffffffffffffda RBX: 000000000000000b RCX: 0000000020000140
  RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
  RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000296 R12: 0000000000000000
  R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
   </TASK>

  Allocated by task 5387:
   kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
   kasan_save_track+0x14/0x30 mm/kasan/common.c:68
   poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
   __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
   kmalloc_noprof include/linux/slab.h:878 [inline]
   kzalloc_noprof include/linux/slab.h:1014 [inline]
   subflow_create_ctx+0x87/0x2a0 net/mptcp/subflow.c:1803
   subflow_ulp_init+0xc3/0x4d0 net/mptcp/subflow.c:1956
   __tcp_set_ulp net/ipv4/tcp_ulp.c:146 [inline]
   tcp_set_ulp+0x326/0x7f0 net/ipv4/tcp_ulp.c:167
   mptcp_subflow_create_socket+0x4ae/0x10a0 net/mptcp/subflow.c:1764
   __mptcp_subflow_connect+0x3cc/0x1490 net/mptcp/subflow.c:1592
   mptcp_pm_create_subflow_or_signal_addr+0xbda/0x23a0 net/mptcp/pm_netlink.c:642
   mptcp_pm_nl_fully_established net/mptcp/pm_netlink.c:650 [inline]
   mptcp_pm_nl_work+0x3a1/0x4f0 net/mptcp/pm_netlink.c:943
   mptcp_worker+0x15a/0x1240 net/mptcp/protocol.c:2777
   process_one_work+0x958/0x1b30 kernel/workqueue.c:3229
   process_scheduled_works kernel/workqueue.c:3310 [inline]
   worker_thread+0x6c8/0xf00 kernel/workqueue.c:3391
   kthread+0x2c1/0x3a0 kernel/kthread.c:389
   ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

  Freed by task 113:
   kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
   kasan_save_track+0x14/0x30 mm/kasan/common.c:68
   kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:579
   poison_slab_object mm/kasan/common.c:247 [inline]
   __kasan_slab_free+0x51/0x70 mm/kasan/common.c:264
   kasan_slab_free include/linux/kasan.h:230 [inline]
   slab_free_hook mm/slub.c:2342 [inline]
   slab_free mm/slub.c:4579 [inline]
   kfree+0x14f/0x4b0 mm/slub.c:4727
   kvfree+0x47/0x50 mm/util.c:701
   kvfree_rcu_list+0xf5/0x2c0 kernel/rcu/tree.c:3423
   kvfree_rcu_drain_ready kernel/rcu/tree.c:3563 [inline]
   kfree_rcu_monitor+0x503/0x8b0 kernel/rcu/tree.c:3632
   kfree_rcu_shrink_scan+0x245/0x3a0 kernel/rcu/tree.c:3966
   do_shrink_slab+0x44f/0x11c0 mm/shrinker.c:435
   shrink_slab+0x32b/0x12a0 mm/shrinker.c:662
   shrink_one+0x47e/0x7b0 mm/vmscan.c:4818
   shrink_many mm/vmscan.c:4879 [inline]
   lru_gen_shrink_node mm/vmscan.c:4957 [inline]
   shrink_node+0x2452/0x39d0 mm/vmscan.c:5937
   kswapd_shrink_node mm/vmscan.c:6765 [inline]
   balance_pgdat+0xc19/0x18f0 mm/vmscan.c:6957
   kswapd+0x5ea/0xbf0 mm/vmscan.c:7226
   kthread+0x2c1/0x3a0 kernel/kthread.c:389
   ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

  Last potentially related work creation:
   kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
   __kasan_record_aux_stack+0xba/0xd0 mm/kasan/generic.c:541
   kvfree_call_rcu+0x74/0xbe0 kernel/rcu/tree.c:3810
   subflow_ulp_release+0x2ae/0x350 net/mptcp/subflow.c:2009
   tcp_cleanup_ulp+0x7c/0x130 net/ipv4/tcp_ulp.c:124
   tcp_v4_destroy_sock+0x1c5/0x6a0 net/ipv4/tcp_ipv4.c:2541
   inet_csk_destroy_sock+0x1a3/0x440 net/ipv4/inet_connection_sock.c:1293
   tcp_done+0x252/0x350 net/ipv4/tcp.c:4870
   tcp_rcv_state_process+0x379b/0x4f30 net/ipv4/tcp_input.c:6933
   tcp_v4_do_rcv+0x1ad/0xa90 net/ipv4/tcp_ipv4.c:1938
   sk_backlog_rcv include/net/sock.h:1115 [inline]
   __release_sock+0x31b/0x400 net/core/sock.c:3072
   __tcp_close+0x4f3/0xff0 net/ipv4/tcp.c:3142
   __mptcp_close_ssk+0x331/0x14d0 net/mptcp/protocol.c:2489
   mptcp_close_ssk net/mptcp/protocol.c:2543 [inline]
   mptcp_close_ssk+0x150/0x220 net/mptcp/protocol.c:2526
   mptcp_pm_nl_rm_addr_or_subflow+0x2be/0xcc0 net/mptcp/pm_netlink.c:878
   mptcp_pm_nl_rm_subflow_received net/mptcp/pm_netlink.c:914 [inline]
   mptcp_nl_remove_id_zero_address+0x305/0x4a0 net/mptcp/pm_netlink.c:1572
   mptcp_pm_nl_del_addr_doit+0x5c9/0x770 net/mptcp/pm_netlink.c:1603
   genl_family_rcv_msg_doit+0x202/0x2f0 net/netlink/genetlink.c:1115
   genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
   genl_rcv_msg+0x565/0x800 net/netlink/genetlink.c:1210
   netlink_rcv_skb+0x165/0x410 net/netlink/af_netlink.c:2551
   genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
   netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
   netlink_unicast+0x53c/0x7f0 net/netlink/af_netlink.c:1357
   netlink_sendmsg+0x8b8/0xd70 net/netlink/af_netlink.c:1901
   sock_sendmsg_nosec net/socket.c:729 [inline]
   __sock_sendmsg net/socket.c:744 [inline]
   ____sys_sendmsg+0x9ae/0xb40 net/socket.c:2607
   ___sys_sendmsg+0x135/0x1e0 net/socket.c:2661
   __sys_sendmsg+0x117/0x1f0 net/socket.c:2690
   do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
   __do_fast_syscall_32+0x73/0x120 arch/x86/entry/common.c:386
   do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
   entry_SYSENTER_compat_after_hwframe+0x84/0x8e

  The buggy address belongs to the object at ffff8880569ac800
   which belongs to the cache kmalloc-512 of size 512
  The buggy address is located 88 bytes inside of
   freed 512-byte region [ffff8880569ac800, ffff8880569aca00)

  The buggy address belongs to the physical page:
  page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x569ac
  head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
  flags: 0x4fff00000000040(head|node=1|zone=1|lastcpupid=0x7ff)
  page_type: f5(slab)
  raw: 04fff00000000040 ffff88801ac42c80 dead000000000100 dead000000000122
  raw: 0000000000000000 0000000080100010 00000001f5000000 0000000000000000
  head: 04fff00000000040 ffff88801ac42c80 dead000000000100 dead000000000122
  head: 0000000000000000 0000000080100010 00000001f5000000 0000000000000000
  head: 04fff00000000002 ffffea00015a6b01 ffffffffffffffff 0000000000000000
  head: 0000000000000004 0000000000000000 00000000ffffffff 0000000000000000
  page dumped because: kasan: bad access detected
  page_owner tracks the page as allocated
  page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 10238, tgid 10238 (kworker/u32:6), ts 597403252405, free_ts 597177952947
   set_page_owner include/linux/page_owner.h:32 [inline]
   post_alloc_hook+0x2d1/0x350 mm/page_alloc.c:1537
   prep_new_page mm/page_alloc.c:1545 [inline]
   get_page_from_freelist+0x101e/0x3070 mm/page_alloc.c:3457
   __alloc_pages_noprof+0x223/0x25a0 mm/page_alloc.c:4733
   alloc_pages_mpol_noprof+0x2c9/0x610 mm/mempolicy.c:2265
   alloc_slab_page mm/slub.c:2412 [inline]
   allocate_slab mm/slub.c:2578 [inline]
   new_slab+0x2ba/0x3f0 mm/slub.c:2631
   ___slab_alloc+0xd1d/0x16f0 mm/slub.c:3818
   __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3908
   __slab_alloc_node mm/slub.c:3961 [inline]
   slab_alloc_node mm/slub.c:4122 [inline]
   __kmalloc_cache_noprof+0x2c5/0x310 mm/slub.c:4290
   kmalloc_noprof include/linux/slab.h:878 [inline]
   kzalloc_noprof include/linux/slab.h:1014 [inline]
   mld_add_delrec net/ipv6/mcast.c:743 [inline]
   igmp6_leave_group net/ipv6/mcast.c:2625 [inline]
   igmp6_group_dropped+0x4ab/0xe40 net/ipv6/mcast.c:723
   __ipv6_dev_mc_dec+0x281/0x360 net/ipv6/mcast.c:979
   addrconf_leave_solict net/ipv6/addrconf.c:2253 [inline]
   __ipv6_ifa_notify+0x3f6/0xc30 net/ipv6/addrconf.c:6283
   addrconf_ifdown.isra.0+0xef9/0x1a20 net/ipv6/addrconf.c:3982
   addrconf_notify+0x220/0x19c0 net/ipv6/addrconf.c:3781
   notifier_call_chain+0xb9/0x410 kernel/notifier.c:93
   call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:1996
   call_netdevice_notifiers_extack net/core/dev.c:2034 [inline]
   call_netdevice_notifiers net/core/dev.c:2048 [inline]
   dev_close_many+0x333/0x6a0 net/core/dev.c:1589
  page last free pid 13136 tgid 13136 stack trace:
   reset_page_owner include/linux/page_owner.h:25 [inline]
   free_pages_prepare mm/page_alloc.c:1108 [inline]
   free_unref_page+0x5f4/0xdc0 mm/page_alloc.c:2638
   stack_depot_save_flags+0x2da/0x900 lib/stackdepot.c:666
   kasan_save_stack+0x42/0x60 mm/kasan/common.c:48
   kasan_save_track+0x14/0x30 mm/kasan/common.c:68
   unpoison_slab_object mm/kasan/common.c:319 [inline]
   __kasan_slab_alloc+0x89/0x90 mm/kasan/common.c:345
   kasan_slab_alloc include/linux/kasan.h:247 [inline]
   slab_post_alloc_hook mm/slub.c:4085 [inline]
   slab_alloc_node mm/slub.c:4134 [inline]
   kmem_cache_alloc_noprof+0x121/0x2f0 mm/slub.c:4141
   skb_clone+0x190/0x3f0 net/core/skbuff.c:2084
   do_one_broadcast net/netlink/af_netlink.c:1462 [inline]
   netlink_broadcast_filtered+0xb11/0xef0 net/netlink/af_netlink.c:1540
   netlink_broadcast+0x39/0x50 net/netlink/af_netlink.c:1564
   uevent_net_broadcast_untagged lib/kobject_uevent.c:331 [inline]
   kobject_uevent_net_broadcast lib/kobject_uevent.c:410 [inline]
   kobject_uevent_env+0xacd/0x1670 lib/kobject_uevent.c:608
   device_del+0x623/0x9f0 drivers/base/core.c:3882
   snd_card_disconnect.part.0+0x58a/0x7c0 sound/core/init.c:546
   snd_card_disconnect+0x1f/0x30 sound/core/init.c:495
   snd_usx2y_disconnect+0xe9/0x1f0 sound/usb/usx2y/usbusx2y.c:417
   usb_unbind_interface+0x1e8/0x970 drivers/usb/core/driver.c:461
   device_remove drivers/base/dd.c:569 [inline]
   device_remove+0x122/0x170 drivers/base/dd.c:561

That's because 'subflow' is used just after 'mptcp_close_ssk(subflow)',
which will initiate the release of its memory. Even if it is very likely
the release and the re-utilisation will be done later on, it is of
course better to avoid any issues and read the content of 'subflow'
before closing it.

Fixes: 1c1f72137598 ("mptcp: pm: only decrement add_addr_accepted for MPJ req")
Cc: stable@vger.kernel.org
Reported-by: syzbot+3c8b7a8e7df6a2a226ca@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/670d7337.050a0220.4cbc0.004f.GAE@google.com
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Link: https://patch.msgid.link/20241015-net-mptcp-uaf-pm-rm-v1-1-c4ee5d987a64@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 1a78998fe1f4..db586a5b3866 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -873,12 +873,12 @@ static void mptcp_pm_nl_rm_addr_or_subflow(struct mptcp_sock *msk,
 				 i, rm_id, id, remote_id, msk->mpc_endpoint_id);
 			spin_unlock_bh(&msk->pm.lock);
 			mptcp_subflow_shutdown(sk, ssk, how);
+			removed |= subflow->request_join;
 
 			/* the following takes care of updating the subflows counter */
 			mptcp_close_ssk(sk, ssk, subflow);
 			spin_lock_bh(&msk->pm.lock);
 
-			removed |= subflow->request_join;
 			if (rm_type == MPTCP_MIB_RMSUBFLOW)
 				__MPTCP_INC_STATS(sock_net(sk), rm_type);
 		}