Re: Private message regarding: [syzbot] [pci?] WARNING in pci_scan_single_device (2)

[syzbot <syzbot+87bb32e345aa80c0554b@syzkaller.appspotmail.com>]

> #syz test
>
> From: Arnav Kapoor <kapoorarnav43@gmail.com>
> Date: Tue, 21 Jan 2026 05:30:00 +0530
> Subject: [PATCH] PCI: Replace WARN_ON with proper error handling in 
> pci_device_add
>
> The WARN_ON macro in pci_device_add triggers kernel warnings when 
> device_add()
> fails due to memory pressure or error injection. This is inappropriate for
> normal error conditions that can occur in fuzzing scenarios.
>
> Replace WARN_ON with proper error handling and logging:
> - Convert firmware device_add failure to error logging
> - Convert kernel device_add failure to error logging and cleanup
> - Properly handle failure cases without triggering spurious warnings
>
> Reported-by: syzbot+87bb32e345aa80c0554b@syzkaller.appspotmail.com
> Signed-off-by: Arnav Kapoor <kapoorarnav43@gmail.com>
> ---
>  drivers/pci/probe.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 669e7c519..9238ec951 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2795,16 +2795,26 @@ void pci_device_add(struct pci_dev *dev, struct 
> pci_bus *bus)
>      ret = pcibios_device_add(dev);
> - WARN_ON(ret < 0);
> + if (ret < 0) {
> + pci_warn(dev, "pcibios_device_add failed\n");
> + }
>  
>      /* Set up MSI IRQ domain */
>      pci_set_msi_domain(dev);
>  
>      /* Notifier could use PCI capabilities */
>      ret = device_add(&dev->dev);
> - WARN_ON(ret < 0);
> + if (ret < 0) {
> + pci_warn(dev, "device_add failed\n");
> + /* Clean up the device from the bus list */
> + down_write(&pci_bus_sem);
> + list_del(&dev->bus_list);
> + up_write(&pci_bus_sem);
> + return;
> + }
>  
>      /* Establish pdev->tsm for newly added (e.g. new SR-IOV VFs) */
>      pci_tsm_init(dev);
>  
>      pci_npem_create(dev);
>  
>      pci_doe_sysfs_init(dev);
>  }
>  
> --
> 2.43.0
>
> On Wednesday, 21 January 2026 at 05:38:30 UTC+5:30 syzbot wrote:
>
> Hello, 
>
> syzbot found the following issue on: 
>
> HEAD commit: 983d014aafb1 kernel: modules: Add SPDX license identifier .. 
> git tree: upstream 
> console output: https://syzkaller.appspot.com/x/log.txt?x=10658852580000 
> kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be 
> dashboard link: https://syzkaller.appspot.com/bug?extid=87bb32e345aa80c0554b 
> compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for 
> Debian) 2.40 
>
> Unfortunately, I don't have any reproducer for this issue yet. 
>
> Downloadable assets: 
> disk image: 
> https://storage.googleapis.com/syzbot-assets/8a294469166c/disk-983d014a.raw.xz 
> vmlinux: 
> https://storage.googleapis.com/syzbot-assets/f9504a6df5a7/vmlinux-983d014a.xz 
> kernel image: 
> https://storage.googleapis.com/syzbot-assets/88a1d939d6af/bzImage-983d014a.xz 
>
> IMPORTANT: if you fix the issue, please add the following tag to the 
> commit: 
> Reported-by: syzbot+87bb32...@syzkaller.appspotmail.com 
>
> ------------[ cut here ]------------ 
> WARNING: drivers/pci/probe.c:2800 at pci_device_add+0x105e/0x1490 
> drivers/pci/probe.c:2800, CPU#0: syz.5.1730/14510 
> Modules linked in: 
> CPU: 0 UID: 0 PID: 14510 Comm: syz.5.1730 Tainted: G U L syzkaller #0 
> PREEMPT(full) 
> Tainted: [U]=USER, [L]=SOFTLOCKUP 
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS 
> Google 10/25/2025 
> RIP: 0010:pci_device_add+0x105e/0x1490 drivers/pci/probe.c:2800 
> Code: e5 04 83 e0 8f 09 e8 88 83 c0 00 00 00 e9 ef f2 ff ff e8 85 7a d6 fc 
> 90 0f 0b 90 90 0f 0b 90 e9 ee f4 ff ff e8 73 7a d6 fc 90 <0f> 0b 90 e9 c1 
> f7 ff ff e8 65 7a d6 fc 90 0f 0b 90 e9 54 f7 ff ff 
> RSP: 0018:ffffc9000bb5f938 EFLAGS: 00010283 
> RAX: 000000000003659d RBX: 00000000fffffff4 RCX: ffffc90015bd3000 
> RDX: 0000000000080000 RSI: ffffffff84e7e38d RDI: 0000000000000005 
> RBP: ffff88801bae0400 R08: 0000000000000005 R09: 0000000000000000 
> R10: 00000000fffffff4 R11: ffffffff81000130 R12: ffff888142e87028 
> R13: ffff888142e87000 R14: 0000000000000001 R15: ffff888142ea2000 
> FS: 00007fa6b528e6c0(0000) GS:ffff8881248f9000(0000) knlGS:0000000000000000 
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 
> CR2: 000020000058e000 CR3: 000000007e2d4000 CR4: 00000000003526f0 
> Call Trace: 
> <TASK> 
> pci_scan_single_device drivers/pci/probe.c:2824 [inline] 
> pci_scan_single_device+0x252/0x310 drivers/pci/probe.c:2810 
> pci_scan_slot+0x1c0/0x760 drivers/pci/probe.c:2907 
> pci_scan_child_bus_extend+0x6b/0x7d0 drivers/pci/probe.c:3126 
> pci_scan_child_bus drivers/pci/probe.c:3239 [inline] 
> pci_rescan_bus+0x18/0x40 drivers/pci/probe.c:3530 
> rescan_store+0xfb/0x130 drivers/pci/pci-sysfs.c:472 
> bus_attr_store+0x74/0xb0 drivers/base/bus.c:172 
> sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:142 
> kernfs_fop_write_iter+0x3af/0x570 fs/kernfs/file.c:352 
> new_sync_write fs/read_write.c:593 [inline] 
> vfs_write+0x7d3/0x11d0 fs/read_write.c:686 
> ksys_write+0x12a/0x250 fs/read_write.c:738 
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] 
> do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94 
> entry_SYSCALL_64_after_hwframe+0x77/0x7f 
> RIP: 0033:0x7fa6b438f7c9 
> 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:00007fa6b528e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 
> RAX: ffffffffffffffda RBX: 00007fa6b45e5fa0 RCX: 00007fa6b438f7c9 
> RDX: 0000000000000001 RSI: 0000200000000200 RDI: 0000000000000003 
> RBP: 00007fa6b4413f91 R08: 0000000000000000 R09: 0000000000000000 
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 
> R13: 00007fa6b45e6038 R14: 00007fa6b45e5fa0 R15: 00007ffd9a287b48 
> </TASK> 
>
>
> --- 
> 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. 
>
> If the report is already addressed, let syzbot know by replying with: 
> #syz fix: exact-commit-title 
>
> 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 
>

Command #1:
This crash does not have a reproducer. I cannot test it.