[syzbot] [net?] BUG: unable to handle kernel paging request in nsim_drv_port_add (2)
From: syzbot
Date: Sun Nov 01 2026 - 02:01:57 EST
Hello,
syzbot found the following issue on:
HEAD commit: 36aad21d50d1 Merge tag 'ksmbd-for-7.4-rc1-part2' of git://..
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1332b159580000
kernel config: https://syzkaller.appspot.com/x/.config?x=dc4462df6d1062fe
dashboard link: https://syzkaller.appspot.com/bug?extid=b3fca27eb4005f0111f4
compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1194b795580000
AI-generated root cause summary:
In netdevsim, sysfs device attributes such as 'new_port' and 'del_port' are
exposed at the device level on nsim_bus_dev without holding device_lock or
checking if the driver is bound. An access via sysfs after the driver has been
unbound, after a failed probe, or concurrently with device removal finds drvdata
set to NULL; passing this NULL pointer to priv_to_devlink() computes a negative
offset from NULL, triggering a kernel page fault crash when attempting to
acquire devlink->lock.
full analysis: https://syzkaller.appspot.com/x/ai_root_cause?x=b3fca27eb4005f0111f4
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b3fca27eb4005f0111f4@xxxxxxxxxxxxxxxxxxxxxxxxx
BUG: unable to handle page fault for address: fffffffffffffeb0
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD f1b3067 P4D f1b3067 PUD f1b5067 PMD 0
Oops: Oops: 0000 [#1] SMP KASAN PTI
CPU: 0 UID: 0 PID: 6031 Comm: syz-executor405 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/15/2026
RIP: 0010:__lock_acquire+0x41/0x2de0 kernel/locking/lockdep.c:5140
Code: 2d 12 48 89 84 24 e0 00 00 00 65 48 8b 05 0f e3 2d 12 48 89 44 24 08 45 31 f6 83 3d 28 dc 32 0f 00 0f 84 90 14 00 00 48 89 fb <48> 8b 07 48 3d a0 69 92 94 0f 84 7e 14 00 00 45 89 cd 89 cd 41 89
RSP: 0018:ffffc900046978d8 EFLAGS: 00010002
RAX: ffff88801ff11f40 RBX: fffffffffffffeb0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: fffffffffffffeb0
RBP: ffff88801ff11f40 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000100 R11: 0000000000000007 R12: fffffffffffffeb0
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000246
FS: 000055558a5ef400(0000) GS:ffff888124716000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffffffffffeb0 CR3: 00000000452a0000 CR4: 00000000003526f0
Call Trace:
<TASK>
lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
__mutex_lock_common kernel/locking/rtmutex_api.c:561 [inline]
mutex_lock_nested+0x55/0x1d0 kernel/locking/rtmutex_api.c:580
nsim_drv_port_add+0x5a/0x140 drivers/net/netdevsim/dev.c:1760
new_port_store+0x1a5/0x280 drivers/net/netdevsim/bus.c:96
kernfs_fop_write_iter+0x3a5/0x540 fs/kernfs/file.c:345
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x61e/0xbb0 fs/read_write.c:687
ksys_write+0x156/0x270 fs/read_write.c:739
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7efc00506777
Code: 48 89 fa 4c 89 df e8 58 1c 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007fff1f51a010 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000055558a5ef400 RCX: 00007efc00506777
RDX: 0000000000000002 RSI: 00007efc005586de RDI: 0000000000000003
RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 00007fff1f51a228
R13: 0000000000000002 R14: 00007efc005825a0 R15: 0000000000000002
</TASK>
Modules linked in:
CR2: fffffffffffffeb0
---[ end trace 0000000000000000 ]---
RIP: 0010:__lock_acquire+0x41/0x2de0 kernel/locking/lockdep.c:5140
Code: 2d 12 48 89 84 24 e0 00 00 00 65 48 8b 05 0f e3 2d 12 48 89 44 24 08 45 31 f6 83 3d 28 dc 32 0f 00 0f 84 90 14 00 00 48 89 fb <48> 8b 07 48 3d a0 69 92 94 0f 84 7e 14 00 00 45 89 cd 89 cd 41 89
RSP: 0018:ffffc900046978d8 EFLAGS: 00010002
RAX: ffff88801ff11f40 RBX: fffffffffffffeb0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: fffffffffffffeb0
RBP: ffff88801ff11f40 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000100 R11: 0000000000000007 R12: fffffffffffffeb0
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000246
FS: 000055558a5ef400(0000) GS:ffff888124716000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffffffffffeb0 CR3: 00000000452a0000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
0: 2d 12 48 89 84 sub $0x84894812,%eax
5: 24 e0 and $0xe0,%al
7: 00 00 add %al,(%rax)
9: 00 65 48 add %ah,0x48(%rbp)
c: 8b 05 0f e3 2d 12 mov 0x122de30f(%rip),%eax # 0x122de321
12: 48 89 44 24 08 mov %rax,0x8(%rsp)
17: 45 31 f6 xor %r14d,%r14d
1a: 83 3d 28 dc 32 0f 00 cmpl $0x0,0xf32dc28(%rip) # 0xf32dc49
21: 0f 84 90 14 00 00 je 0x14b7
27: 48 89 fb mov %rdi,%rbx
* 2a: 48 8b 07 mov (%rdi),%rax <-- trapping instruction
2d: 48 3d a0 69 92 94 cmp $0xffffffff949269a0,%rax
33: 0f 84 7e 14 00 00 je 0x14b7
39: 45 89 cd mov %r9d,%r13d
3c: 89 cd mov %ecx,%ebp
3e: 41 rex.B
3f: 89 .byte 0x89
---
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