[syzbot] [smc?] general protection fault in __smc_diag_dump (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 5aca7966d2a7 Merge tag 'perf-tools-fixes-for-v6.17-2025-09..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=147e2e42580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8f01d8629880e620
dashboard link: https://syzkaller.appspot.com/bug?extid=f775be4458668f7d220e
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=17aec534580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=115a9f62580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f191b2524020/disk-5aca7966.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5aa02ba0cba2/vmlinux-5aca7966.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b9b04ddba61b/bzImage-5aca7966.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f775be...@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xfbd5a5d5a0000003: 0000 [#1] SMP KASAN NOPTI
KASAN: maybe wild-memory-access in range [0xdead4ead00000018-0xdead4ead0000001f]
CPU: 1 UID: 0 PID: 6949 Comm: syz.0.335 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:smc_diag_msg_common_fill net/smc/smc_diag.c:44 [inline]
RIP: 0010:__smc_diag_dump.constprop.0+0x3ca/0x2550 net/smc/smc_diag.c:89
Code: 4c 8b b3 40 06 00 00 4d 85 f6 0f 84 f6 02 00 00 e8 6b 4f 78 f6 49 8d 7e 18 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 f6 1e 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b
RSP: 0018:ffffc90003f2f1a8 EFLAGS: 00010a06
RAX: dffffc0000000000 RBX: ffff88802a33bd40 RCX: ffffffff897ee8a4
RDX: 1bd5a9d5a0000003 RSI: ffffffff8b434dd5 RDI: dead4ead00000018
RBP: ffff888032418000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000080000001 R11: 0000000000000000 R12: ffff8880754915f0
R13: ffff88805d823780 R14: dead4ead00000000 R15: ffff88802a33c380
FS: 00007fec5f7dd6c0(0000) GS:ffff8881247b2000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fec5f7dcf98 CR3: 000000007d646000 CR4: 00000000003526f0
Call Trace:
<TASK>
smc_diag_dump_proto+0x26d/0x420 net/smc/smc_diag.c:217
smc_diag_dump+0x27/0x90 net/smc/smc_diag.c:234
netlink_dump+0x539/0xd30 net/netlink/af_netlink.c:2327
__netlink_dump_start+0x6d6/0x990 net/netlink/af_netlink.c:2442
netlink_dump_start include/linux/netlink.h:341 [inline]
smc_diag_handler_dump+0x1f9/0x240 net/smc/smc_diag.c:251
__sock_diag_cmd net/core/sock_diag.c:249 [inline]
sock_diag_rcv_msg+0x438/0x790 net/core/sock_diag.c:285
netlink_rcv_skb+0x158/0x420 net/netlink/af_netlink.c:2552
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0x5a7/0x870 net/netlink/af_netlink.c:1346
netlink_sendmsg+0x8d1/0xdd0 net/netlink/af_netlink.c:1896
sock_sendmsg_nosec net/socket.c:714 [inline]
__sock_sendmsg net/socket.c:729 [inline]
____sys_sendmsg+0xa95/0xc70 net/socket.c:2614
___sys_sendmsg+0x134/0x1d0 net/socket.c:2668
__sys_sendmsg+0x16d/0x220 net/socket.c:2700
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fec6018eba9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fec5f7dd038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fec603d6090 RCX: 00007fec6018eba9
RDX: 0000000000000000 RSI: 0000200000000140 RDI: 0000000000000003
RBP: 00007fec60211e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fec603d6128 R14: 00007fec603d6090 R15: 00007ffcb0713c08
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:smc_diag_msg_common_fill net/smc/smc_diag.c:44 [inline]
RIP: 0010:__smc_diag_dump.constprop.0+0x3ca/0x2550 net/smc/smc_diag.c:89
Code: 4c 8b b3 40 06 00 00 4d 85 f6 0f 84 f6 02 00 00 e8 6b 4f 78 f6 49 8d 7e 18 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 f6 1e 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b
RSP: 0018:ffffc90003f2f1a8 EFLAGS: 00010a06
RAX: dffffc0000000000 RBX: ffff88802a33bd40 RCX: ffffffff897ee8a4
RDX: 1bd5a9d5a0000003 RSI: ffffffff8b434dd5 RDI: dead4ead00000018
RBP: ffff888032418000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000080000001 R11: 0000000000000000 R12: ffff8880754915f0
R13: ffff88805d823780 R14: dead4ead00000000 R15: ffff88802a33c380
FS: 00007fec5f7dd6c0(0000) GS:ffff8881247b2000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fec5f7dcf98 CR3: 000000007d646000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
0: 4c 8b b3 40 06 00 00 mov 0x640(%rbx),%r14
7: 4d 85 f6 test %r14,%r14
a: 0f 84 f6 02 00 00 je 0x306
10: e8 6b 4f 78 f6 call 0xf6784f80
15: 49 8d 7e 18 lea 0x18(%r14),%rdi
19: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
20: fc ff df
23: 48 89 fa mov %rdi,%rdx
26: 48 c1 ea 03 shr $0x3,%rdx
* 2a: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
2e: 0f 85 f6 1e 00 00 jne 0x1f2a
34: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
3b: fc ff df
3e: 4d rex.WRB
3f: 8b .byte 0x8b


---
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syzbot engineers can be reached at syzk...@googlegroups.com.

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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
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#syz dup: exact-subject-of-another-report

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#syz undup

[syzbot]

syzbot has bisected this issue to:

commit 98d4435efcbf37801a3246fb53856c4b934a2613
Author: Jeongjun Park <aha3...@gmail.com>
Date: Thu Aug 29 03:56:48 2024 +0000

net/smc: prevent NULL pointer dereference in txopt_get

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=131dc712580000
start commit: 5aca7966d2a7 Merge tag 'perf-tools-fixes-for-v6.17-2025-09..
git tree: upstream
final oops: https://syzkaller.appspot.com/x/report.txt?x=109dc712580000
console output: https://syzkaller.appspot.com/x/log.txt?x=171dc712580000

kernel config: https://syzkaller.appspot.com/x/.config?x=8f01d8629880e620
dashboard link: https://syzkaller.appspot.com/bug?extid=f775be4458668f7d220e

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17aec534580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=115a9f62580000

Reported-by: syzbot+f775be...@syzkaller.appspotmail.com
Fixes: 98d4435efcbf ("net/smc: prevent NULL pointer dereference in txopt_get")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[Wang Liang]

This issue is similar to:
https://lore.kernel.org/netdev/20250331081003.150...@huawei.com/

The process like this:
(CPU1)                           | (CPU2)
---------------------------------|-------------------------------
inet_create()                    |
  sk = sk_alloc()                |
                                 |
  inet_init_csk_locks()          |
    modify smc->clcsock          |
                                 |
  sk->sk_prot->init              |
    smc_inet_init_sock()         |
      smc_sk_init()              |
        smc_hash_sk()            |
          head = &smc_hash->ht;  |
          sk_add_node(sk, head); |
                                 | smc_diag_dump_proto
                                 |   head = &smc_hash->ht;
                                 |     sk_for_each(sk, head)
                                 |       __smc_diag_dump()
                                 |         visit smc->clcsock


The 'smc->clcsock' is modified in inet_init_csk_locks():
__sock_create(family=2, type=1, protocol=256)
    inet_create
        sk = sk_alloc(...); // smc->clcsock = 0
        inet_init_csk_locks(sk);
            icsk = inet_csk(sk);
spin_lock_init(&icsk->icsk_accept_queue.rskq_lock); // smc->clcsock =
0xdead4ead00000000

The relevant structure is 'struct smc_sock' and 'struct
inet_connection_sock':
struct smc_sock {
    union {
        struct sock      sk;
        struct inet_sock icsk_inet;
    };
    struct socket        *clcsock;
    ...
};
struct inet_connection_sock {
    struct inet_sock          icsk_inet;
    struct request_sock_queue icsk_accept_queue;
    ...
};

Commit 60ada4fe644e ("smc: Fix various oops due to inet_sock type
confusion.")
add inet_sock as the first member of smc_sock. Maybe add
inet_connection_sock
instead of inet_sock is more appropriate.

#syz test

From 782467e7f55f2f1487744252060ffbaa992ee47a Mon Sep 17 00:00:00 2001
From: Wang Liang <wangl...@huawei.com>
Date: Sat, 20 Sep 2025 11:29:52 +0800
Subject: [PATCH net] net/smc: fix general protection fault in
__smc_diag_dump

Use inet_connection_sock instead of inet_sock in struct smc_sock.

Signed-off-by: Wang Liang <wangl...@huawei.com>
---
 net/smc/smc.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/smc/smc.h b/net/smc/smc.h
index 2c9084963739..1b20f0c927d3 100644
--- a/net/smc/smc.h
+++ b/net/smc/smc.h
@@ -285,7 +285,7 @@ struct smc_connection {
 struct smc_sock {                              /* smc sock container */
        union {
                struct sock             sk;
-               struct inet_sock        icsk_inet;
+               struct inet_connection_sock     inet_conn;
        };
        struct socket           *clcsock;       /* internal tcp socket */
        void                    (*clcsk_state_change)(struct sock *sk);
--
2.34.1

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

failed to apply patch:
checking file net/smc/smc.h
Hunk #1 FAILED at 285.
1 out of 1 hunk FAILED



Tested on:

commit: cd89d487 Merge tag '6.17-rc6-smb3-client-fixes' of git..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=8f01d8629880e620
dashboard link: https://syzkaller.appspot.com/bug?extid=f775be4458668f7d220e
compiler:

patch: https://syzkaller.appspot.com/x/patch.diff?x=1381a0e2580000

[Wang Liang]

#syz test

[syzbot]

Hello,

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

Reported-by: syzbot+f775be...@syzkaller.appspotmail.com
Tested-by: syzbot+f775be...@syzkaller.appspotmail.com

Tested on:

commit: cd89d487 Merge tag '6.17-rc6-smb3-client-fixes' of git..
git tree: upstream

console output: https://syzkaller.appspot.com/x/log.txt?x=10864d04580000

kernel config: https://syzkaller.appspot.com/x/.config?x=8f01d8629880e620
dashboard link: https://syzkaller.appspot.com/bug?extid=f775be4458668f7d220e

compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=102f5c7c580000

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