CVE-2024-50085: mptcp: pm: fix UaF read in mptcp_pm_nl_rm_addr_or_subflow

In the Linux kernel, the following vulnerability has been resolved:

mptcp: pm: fix UaF read in mptcppmnlrmaddrorsubflow

Syzkaller reported this splat:

================================================================== BUG: KASAN: slab-use-after-free in mptcppmnlrmaddrorsubflow+0xb44/0xcc0 net/mptcp/pmnetlink.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> dumpstack lib/dumpstack.c:94 [inline] dumpstacklvl+0x116/0x1f0 lib/dumpstack.c:120 printaddressdescription mm/kasan/report.c:377 [inline] printreport+0xc3/0x620 mm/kasan/report.c:488 kasanreport+0xd9/0x110 mm/kasan/report.c:601 mptcppmnlrmaddrorsubflow+0xb44/0xcc0 net/mptcp/pmnetlink.c:881 mptcppmnlrmsubflowreceived net/mptcp/pmnetlink.c:914 [inline] mptcpnlremoveidzeroaddress+0x305/0x4a0 net/mptcp/pmnetlink.c:1572 mptcppmnldeladdrdoit+0x5c9/0x770 net/mptcp/pmnetlink.c:1603 genlfamilyrcvmsgdoit+0x202/0x2f0 net/netlink/genetlink.c:1115 genlfamilyrcvmsg net/netlink/genetlink.c:1195 [inline] genlrcvmsg+0x565/0x800 net/netlink/genetlink.c:1210 netlinkrcvskb+0x165/0x410 net/netlink/afnetlink.c:2551 genlrcv+0x28/0x40 net/netlink/genetlink.c:1219 netlinkunicastkernel net/netlink/afnetlink.c:1331 [inline] netlinkunicast+0x53c/0x7f0 net/netlink/afnetlink.c:1357 netlinksendmsg+0x8b8/0xd70 net/netlink/afnetlink.c:1901 socksendmsgnosec net/socket.c:729 [inline] socksendmsg net/socket.c:744 [inline] syssendmsg+0x9ae/0xb40 net/socket.c:2607 syssendmsg+0x135/0x1e0 net/socket.c:2661 syssendmsg+0x117/0x1f0 net/socket.c:2690 dosyscall32irqson arch/x86/entry/common.c:165 [inline] dofastsyscall32+0x73/0x120 arch/x86/entry/common.c:386 dofastsyscall32+0x32/0x80 arch/x86/entry/common.c:411 entrySYSENTERcompatafterhwframe+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 ORIGRAX: 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: kasansavestack+0x33/0x60 mm/kasan/common.c:47 kasansavetrack+0x14/0x30 mm/kasan/common.c:68 poisonkmallocredzone mm/kasan/common.c:377 [inline] kasankmalloc+0xaa/0xb0 mm/kasan/common.c:394 kmallocnoprof include/linux/slab.h:878 [inline] kzallocnoprof include/linux/slab.h:1014 [inline] subflowcreatectx+0x87/0x2a0 net/mptcp/subflow.c:1803 subflowulpinit+0xc3/0x4d0 net/mptcp/subflow.c:1956 tcpsetulp net/ipv4/tcpulp.c:146 [inline] tcpsetulp+0x326/0x7f0 net/ipv4/tcpulp.c:167 mptcpsubflowcreatesocket+0x4ae/0x10a0 net/mptcp/subflow.c:1764 mptcpsubflowconnect+0x3cc/0x1490 net/mptcp/subflow.c:1592 mptcppmcreatesubfloworsignaladdr+0xbda/0x23a0 net/mptcp/pmnetlink.c:642 mptcppmnlfullyestablished net/mptcp/pmnetlink.c:650 [inline] mptcppmnlwork+0x3a1/0x4f0 net/mptcp/pmnetlink.c:943 mptcpworker+0x15a/0x1240 net/mptcp/protocol.c:2777 processonework+0x958/0x1b30 kernel/workqueue.c:3229 processscheduledworks kernel/workqueue.c:3310 [inline] workerthread+0x6c8/0xf00 kernel/workqueue.c:3391 kthread+0x2c1/0x3a0 kernel/kthread.c:389 retfromfork+0x45/0x80 arch/x86/ke ---truncated---