[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]

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