[syzbot] [net?] general protection fault in reuseport_add_sock (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 301927d2d2eb Merge tag 'for-net-2024-07-26' of git://git.k..
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=17332fad980000
kernel config: https://syzkaller.appspot.com/x/.config?x=968c4fa762577d3f
dashboard link: https://syzkaller.appspot.com/bug?extid=e6979a5d2f10ecb700e4
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11d0a623980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1538ac55980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cb9ce2729d35/disk-301927d2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/644eaaef61a5/vmlinux-301927d2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2f92322485c3/bzImage-301927d2.xz

The issue was bisected to:

commit 6ba84574026792ce33a40c7da721dea36d0f3973
Author: Xin Long <lucie...@gmail.com>
Date: Mon Nov 12 10:27:17 2018 +0000

sctp: process sk_reuseport in sctp_get_port_local

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14ad25bd980000
final oops: https://syzkaller.appspot.com/x/report.txt?x=16ad25bd980000
console output: https://syzkaller.appspot.com/x/log.txt?x=12ad25bd980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e6979a...@syzkaller.appspotmail.com
Fixes: 6ba845740267 ("sctp: process sk_reuseport in sctp_get_port_local")

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
CPU: 1 UID: 0 PID: 10230 Comm: syz-executor119 Not tainted 6.10.0-syzkaller-12585-g301927d2d2eb #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
RIP: 0010:reuseport_add_sock+0x27e/0x5e0 net/core/sock_reuseport.c:350
Code: 00 0f b7 5d 00 bf 01 00 00 00 89 de e8 1b a4 ff f7 83 fb 01 0f 85 a3 01 00 00 e8 6d a0 ff f7 49 8d 7e 12 48 89 f8 48 c1 e8 03 <42> 0f b6 04 28 84 c0 0f 85 4b 02 00 00 41 0f b7 5e 12 49 8d 7e 14
RSP: 0018:ffffc9000b947c98 EFLAGS: 00010202
RAX: 0000000000000002 RBX: ffff8880252ddf98 RCX: ffff888079478000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000012
RBP: 0000000000000001 R08: ffffffff8993e18d R09: 1ffffffff1fef385
R10: dffffc0000000000 R11: fffffbfff1fef386 R12: ffff8880252ddac0
R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
FS: 00007f24e45b96c0(0000) GS:ffff8880b9300000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffcced5f7b8 CR3: 00000000241be000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
__sctp_hash_endpoint net/sctp/input.c:762 [inline]
sctp_hash_endpoint+0x52a/0x600 net/sctp/input.c:790
sctp_listen_start net/sctp/socket.c:8570 [inline]
sctp_inet_listen+0x767/0xa20 net/sctp/socket.c:8625
__sys_listen_socket net/socket.c:1883 [inline]
__sys_listen+0x1b7/0x230 net/socket.c:1894
__do_sys_listen net/socket.c:1902 [inline]
__se_sys_listen net/socket.c:1900 [inline]
__x64_sys_listen+0x5a/0x70 net/socket.c:1900
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: 0033:0x7f24e46039b9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 91 1a 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f24e45b9228 EFLAGS: 00000246 ORIG_RAX: 0000000000000032
RAX: ffffffffffffffda RBX: 00007f24e468e428 RCX: 00007f24e46039b9
RDX: 00007f24e46039b9 RSI: 0000000000000003 RDI: 0000000000000004
RBP: 00007f24e468e420 R08: 00007f24e45b96c0 R09: 00007f24e45b96c0
R10: 00007f24e45b96c0 R11: 0000000000000246 R12: 00007f24e468e42c
R13: 00007f24e465a5dc R14: 0020000000000001 R15: 00007ffcced5f7d8
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:reuseport_add_sock+0x27e/0x5e0 net/core/sock_reuseport.c:350
Code: 00 0f b7 5d 00 bf 01 00 00 00 89 de e8 1b a4 ff f7 83 fb 01 0f 85 a3 01 00 00 e8 6d a0 ff f7 49 8d 7e 12 48 89 f8 48 c1 e8 03 <42> 0f b6 04 28 84 c0 0f 85 4b 02 00 00 41 0f b7 5e 12 49 8d 7e 14
RSP: 0018:ffffc9000b947c98 EFLAGS: 00010202
RAX: 0000000000000002 RBX: ffff8880252ddf98 RCX: ffff888079478000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000012
RBP: 0000000000000001 R08: ffffffff8993e18d R09: 1ffffffff1fef385
R10: dffffc0000000000 R11: fffffbfff1fef386 R12: ffff8880252ddac0
R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
FS: 00007f24e45b96c0(0000) GS:ffff8880b9300000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffcced5f7b8 CR3: 00000000241be000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 00 0f add %cl,(%rdi)
2: b7 5d mov $0x5d,%bh
4: 00 bf 01 00 00 00 add %bh,0x1(%rdi)
a: 89 de mov %ebx,%esi
c: e8 1b a4 ff f7 call 0xf7ffa42c
11: 83 fb 01 cmp $0x1,%ebx
14: 0f 85 a3 01 00 00 jne 0x1bd
1a: e8 6d a0 ff f7 call 0xf7ffa08c
1f: 49 8d 7e 12 lea 0x12(%r14),%rdi
23: 48 89 f8 mov %rdi,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 0f b6 04 28 movzbl (%rax,%r13,1),%eax <-- trapping instruction
2f: 84 c0 test %al,%al
31: 0f 85 4b 02 00 00 jne 0x282
37: 41 0f b7 5e 12 movzwl 0x12(%r14),%ebx
3c: 49 8d 7e 14 lea 0x14(%r14),%rdi


---
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 syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection

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

[Kuniyuki Iwashima]

From: syzbot <syzbot+e6979a...@syzkaller.appspotmail.com>
Date: Mon, 29 Jul 2024 09:28:29 -0700

Here we need to protect the other sk in the hash table as we do so for
TCP/UDP by taking the hash bucket lock.


#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git 1722389b0d863056d78287a120a1d6cadb8d4f7b

diff --git a/net/core/sock_reuseport.c b/net/core/sock_reuseport.c
index 5a165286e4d8..b1614da1e41c 100644
--- a/net/core/sock_reuseport.c
+++ b/net/core/sock_reuseport.c
@@ -347,6 +347,8 @@ int reuseport_add_sock(struct sock *sk, struct sock *sk2, bool bind_inany)
return -EBUSY;
}

+ WARN_ON(!reuse);
+
if (reuse->num_socks + reuse->num_closed_socks == reuse->max_socks) {
reuse = reuseport_grow(reuse);
if (!reuse) {
diff --git a/net/sctp/input.c b/net/sctp/input.c
index 17fcaa9b0df9..a8a254a5008e 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -735,15 +735,19 @@ static int __sctp_hash_endpoint(struct sctp_endpoint *ep)
struct sock *sk = ep->base.sk;
struct net *net = sock_net(sk);
struct sctp_hashbucket *head;
+ int err = 0;

ep->hashent = sctp_ep_hashfn(net, ep->base.bind_addr.port);
head = &sctp_ep_hashtable[ep->hashent];

+ write_lock(&head->lock);
if (sk->sk_reuseport) {
bool any = sctp_is_ep_boundall(sk);
struct sctp_endpoint *ep2;
struct list_head *list;
- int cnt = 0, err = 1;
+ int cnt = 0;
+
+ err = 1;

list_for_each(list, &ep->base.bind_addr.address_list)
cnt++;
@@ -761,24 +765,24 @@ static int __sctp_hash_endpoint(struct sctp_endpoint *ep)
if (!err) {
err = reuseport_add_sock(sk, sk2, any);
if (err)
- return err;
+ goto out;
break;
} else if (err < 0) {
- return err;
+ goto out;
}
}

if (err) {
err = reuseport_alloc(sk, any);
if (err)
- return err;
+ goto out;
}
}

- write_lock(&head->lock);
hlist_add_head(&ep->node, &head->chain);
+out:
write_unlock(&head->lock);
- return 0;
+ return err;
}

/* Add an endpoint to the hash. Local BH-safe. */
@@ -803,10 +807,9 @@ static void __sctp_unhash_endpoint(struct sctp_endpoint *ep)

head = &sctp_ep_hashtable[ep->hashent];

+ write_lock(&head->lock);
if (rcu_access_pointer(sk->sk_reuseport_cb))
reuseport_detach_sock(sk);
-
- write_lock(&head->lock);
hlist_del_init(&ep->node);
write_unlock(&head->lock);
}

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+e6979a...@syzkaller.appspotmail.com
Tested-by: syzbot+e6979a...@syzkaller.appspotmail.com

Tested on:

commit: 1722389b Merge tag 'net-6.11-rc1' of git://git.kernel...
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1508ede3980000
kernel config: https://syzkaller.appspot.com/x/.config?x=5efb917b1462a973

dashboard link: https://syzkaller.appspot.com/bug?extid=e6979a5d2f10ecb700e4
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=13c648d3980000

Note: testing is done by a robot and is best-effort only.