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Message-ID: <696693f2.a70a0220.245e30.0001.GAE@google.com>
Date: Tue, 13 Jan 2026 10:50:26 -0800
From: syzbot <syzbot+2c42ea4485b29beb0643@...kaller.appspotmail.com>
To: davem@...emloft.net, edumazet@...gle.com, horms@...nel.org, 
	kuba@...nel.org, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, 
	pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [net?] memory leak in l2tp_tunnel_create

Hello,

syzbot found the following issue on:

HEAD commit:    f0b9d8eb98df Merge tag 'nfsd-6.19-3' of git://git.kernel.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1252c19a580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d60836e327fd6756
dashboard link: https://syzkaller.appspot.com/bug?extid=2c42ea4485b29beb0643
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12741074580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15fba922580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/aad2d47ff01d/disk-f0b9d8eb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c31e7ae85c07/vmlinux-f0b9d8eb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5525fab81561/bzImage-f0b9d8eb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2c42ea4485b29beb0643@...kaller.appspotmail.com

BUG: memory leak
unreferenced object 0xffff88811b68c400 (size 256):
  comm "syz.0.17", pid 6086, jiffies 4294944299
  hex dump (first 32 bytes):
    01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc cc18917d):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4958 [inline]
    slab_alloc_node mm/slub.c:5263 [inline]
    __kmalloc_cache_noprof+0x3b2/0x570 mm/slub.c:5771
    kmalloc_noprof include/linux/slab.h:957 [inline]
    kzalloc_noprof include/linux/slab.h:1094 [inline]
    l2tp_tunnel_create+0x55/0x130 net/l2tp/l2tp_core.c:1573
    pppol2tp_tunnel_get+0x134/0x250 net/l2tp/l2tp_ppp.c:653
    pppol2tp_connect+0x234/0x920 net/l2tp/l2tp_ppp.c:710
    __sys_connect_file+0x7a/0xb0 net/socket.c:2089
    __sys_connect+0xde/0x110 net/socket.c:2108
    __do_sys_connect net/socket.c:2114 [inline]
    __se_sys_connect net/socket.c:2111 [inline]
    __x64_sys_connect+0x1c/0x30 net/socket.c:2111
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xf80 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

BUG: memory leak
unreferenced object 0xffff88810a290200 (size 512):
  comm "syz.0.17", pid 6086, jiffies 4294944299
  hex dump (first 32 bytes):
    7d eb 04 0c 00 00 00 00 01 00 00 00 00 00 00 00  }...............
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc babb6a4f):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4958 [inline]
    slab_alloc_node mm/slub.c:5263 [inline]
    __do_kmalloc_node mm/slub.c:5656 [inline]
    __kmalloc_noprof+0x3e0/0x660 mm/slub.c:5669
    kmalloc_noprof include/linux/slab.h:961 [inline]
    kzalloc_noprof include/linux/slab.h:1094 [inline]
    l2tp_session_create+0x3a/0x3b0 net/l2tp/l2tp_core.c:1778
    pppol2tp_connect+0x48b/0x920 net/l2tp/l2tp_ppp.c:755
    __sys_connect_file+0x7a/0xb0 net/socket.c:2089
    __sys_connect+0xde/0x110 net/socket.c:2108
    __do_sys_connect net/socket.c:2114 [inline]
    __se_sys_connect net/socket.c:2111 [inline]
    __x64_sys_connect+0x1c/0x30 net/socket.c:2111
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xf80 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

BUG: memory leak
unreferenced object 0xffff88811b68c500 (size 256):
  comm "syz.0.18", pid 6087, jiffies 4294944299
  hex dump (first 32 bytes):
    01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc a2050c30):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4958 [inline]
    slab_alloc_node mm/slub.c:5263 [inline]
    __kmalloc_cache_noprof+0x3b2/0x570 mm/slub.c:5771
    kmalloc_noprof include/linux/slab.h:957 [inline]
    kzalloc_noprof include/linux/slab.h:1094 [inline]
    l2tp_tunnel_create+0x55/0x130 net/l2tp/l2tp_core.c:1573
    pppol2tp_tunnel_get+0x134/0x250 net/l2tp/l2tp_ppp.c:653
    pppol2tp_connect+0x234/0x920 net/l2tp/l2tp_ppp.c:710
    __sys_connect_file+0x7a/0xb0 net/socket.c:2089
    __sys_connect+0xde/0x110 net/socket.c:2108
    __do_sys_connect net/socket.c:2114 [inline]
    __se_sys_connect net/socket.c:2111 [inline]
    __x64_sys_connect+0x1c/0x30 net/socket.c:2111
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xf80 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

BUG: memory leak
unreferenced object 0xffff88810a290400 (size 512):
  comm "syz.0.18", pid 6087, jiffies 4294944299
  hex dump (first 32 bytes):
    7d eb 04 0c 00 00 00 00 01 00 00 00 00 00 00 00  }...............
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc c3dcc856):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4958 [inline]
    slab_alloc_node mm/slub.c:5263 [inline]
    __do_kmalloc_node mm/slub.c:5656 [inline]
    __kmalloc_noprof+0x3e0/0x660 mm/slub.c:5669
    kmalloc_noprof include/linux/slab.h:961 [inline]
    kzalloc_noprof include/linux/slab.h:1094 [inline]
    l2tp_session_create+0x3a/0x3b0 net/l2tp/l2tp_core.c:1778
    pppol2tp_connect+0x48b/0x920 net/l2tp/l2tp_ppp.c:755
    __sys_connect_file+0x7a/0xb0 net/socket.c:2089
    __sys_connect+0xde/0x110 net/socket.c:2108
    __do_sys_connect net/socket.c:2114 [inline]
    __se_sys_connect net/socket.c:2111 [inline]
    __x64_sys_connect+0x1c/0x30 net/socket.c:2111
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xf80 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

BUG: memory leak
unreferenced object 0xffff88810ac82840 (size 1472):
  comm "syz.0.19", pid 6088, jiffies 4294944300
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 22 0e aa 38 00 00 00 00  ........"..8....
    0a 00 07 40 00 00 00 00 18 ae 57 0a 81 88 ff ff  ...@......W.....
  backtrace (crc 6ae27eda):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4958 [inline]
    slab_alloc_node mm/slub.c:5263 [inline]
    kmem_cache_alloc_noprof+0x3b4/0x590 mm/slub.c:5270
    sk_prot_alloc+0x3e/0x1b0 net/core/sock.c:2239
    sk_alloc+0x36/0x440 net/core/sock.c:2301
    inet6_create net/ipv6/af_inet6.c:193 [inline]
    inet6_create+0x163/0x550 net/ipv6/af_inet6.c:120
    __sock_create+0x1a9/0x310 net/socket.c:1605
    sock_create net/socket.c:1663 [inline]
    __sys_socket_create net/socket.c:1700 [inline]
    __sys_socket+0xb9/0x1a0 net/socket.c:1747
    __do_sys_socket net/socket.c:1761 [inline]
    __se_sys_socket net/socket.c:1759 [inline]
    __x64_sys_socket+0x1b/0x30 net/socket.c:1759
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xf80 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

BUG: memory leak
unreferenced object 0xffff8881285dd800 (size 32):
  comm "syz.0.19", pid 6088, jiffies 4294944300
  hex dump (first 32 bytes):
    f8 52 86 00 81 88 ff ff 00 00 00 00 00 00 00 00  .R..............
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc bad1c2bd):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4958 [inline]
    slab_alloc_node mm/slub.c:5263 [inline]
    __do_kmalloc_node mm/slub.c:5656 [inline]
    __kmalloc_noprof+0x3e0/0x660 mm/slub.c:5669
    kmalloc_noprof include/linux/slab.h:961 [inline]
    kzalloc_noprof include/linux/slab.h:1094 [inline]
    lsm_blob_alloc+0x4d/0x70 security/security.c:192
    lsm_sock_alloc security/security.c:4375 [inline]
    security_sk_alloc+0x2f/0x270 security/security.c:4391
    sk_prot_alloc+0x8f/0x1b0 net/core/sock.c:2248
    sk_alloc+0x36/0x440 net/core/sock.c:2301
    inet6_create net/ipv6/af_inet6.c:193 [inline]
    inet6_create+0x163/0x550 net/ipv6/af_inet6.c:120
    __sock_create+0x1a9/0x310 net/socket.c:1605
    sock_create net/socket.c:1663 [inline]
    __sys_socket_create net/socket.c:1700 [inline]
    __sys_socket+0xb9/0x1a0 net/socket.c:1747
    __do_sys_socket net/socket.c:1761 [inline]
    __se_sys_socket net/socket.c:1759 [inline]
    __x64_sys_socket+0x1b/0x30 net/socket.c:1759
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xf80 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

connection error: failed to recv *flatrpc.ExecutorMessageRawT: EOF


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@...glegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

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