syzbot reported memleak of struct l2tp_session, l2tp_tunnel, sock, etc. [0] The cited commit moved down the validation of the protocol version in l2tp_udp_encap_recv(). The new place requires an extra error handling to avoid the memleak. Let's call l2tp_session_put() there. [0]: 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 Fixes: 364798056f518 ("l2tp: Support different protocol versions with same IP/port quadruple") Reported-by: syzbot+2c42ea4485b29beb0643@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/696693f2.a70a0220.245e30.0001.GAE@google.com/ Signed-off-by: Kuniyuki Iwashima --- net/l2tp/l2tp_core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c index 687c1366a4d0f..70335667ef037 100644 --- a/net/l2tp/l2tp_core.c +++ b/net/l2tp/l2tp_core.c @@ -1086,8 +1086,10 @@ int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb) tunnel = session->tunnel; /* Check protocol version */ - if (version != tunnel->version) + if (version != tunnel->version) { + l2tp_session_put(session); goto invalid; + } if (version == L2TP_HDR_VER_3 && l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr)) { -- 2.52.0.457.g6b5491de43-goog