Re: [PATCH 1/2] firewire: Kill unnecessary buf check in device_attribute.show

Takashi Sakamoto
2024-03-18T04:46:15Z

Hi,

On Mon, Jan 22, 2024 at 05:56:04PM +0900, Takashi Sakamoto wrote:
> Hi,
>
> On Mon, Jan 22, 2024 at 01:39:41PM +0800, Li Zhijian wrote:
> > Per Documentation/filesystems/sysfs.rst:
> > > sysfs allocates a buffer of size (PAGE_SIZE) and passes it to the
> > > method.
> >
> > So we can kill the unnecessary buf check safely.
> >
> > Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
> > ---
> > drivers/firewire/core-device.c | 14 +++-----------
> > 1 file changed, 3 insertions(+), 11 deletions(-)
>
> Applied both patches to linux-next branch, since they are not so-urgent
> fixes.

I realized that it causes an issue at the path to initialize device
structure for node in IEEE 1394 bus.

(drivers/firewire/core-device.c)
fw_device_init() / fw_device_refresh()
->create_units()
->init_fw_attribute_group()
->attr->show(dev, attr, NULL)

kernel: ------------[ cut here ]------------
kernel: invalid sysfs_emit: buf:0000000000000000
kernel: WARNING: CPU: 5 PID: 647501 at fs/sysfs/file.c:747 sysfs_emit+0xb5/0xc0
kernel: Modules linked in: snd_fireworks(OE) snd_firewire_lib(OE) firewire_ohci(OE) firewire_core(OE) cfg80211 veth nft_masq crc_itu_t vfio_pci vfio_pci_core vfio_iommu_type1 vfio iommufd rpcsec_gss_krb5 nfsv4 nfs netfs snd_seq_dummy sn>
kernel: crypto_simd asus_wmi snd_timer ledtrig_audio cryptd cec sparse_keymap nls_iso8859_1 rapl platform_profile wmi_bmof k10temp i2c_piix4 snd rc_core i2c_algo_bit ccp soundcore zfs(PO) spl(O) input_leds joydev cdc_mbim cdc_wdm mac_h>
kernel: CPU: 5 PID: 647501 Comm: kworker/5:0 Tainted: P W OE 6.8.0-11-generic #11-Ubuntu
kernel: Hardware name: System manufacturer System Product Name/TUF GAMING X570-PLUS, BIOS 5003 10/07/2023
kernel: Workqueue: firewire fw_device_workfn [firewire_core]
kernel: RIP: 0010:sysfs_emit+0xb5/0xc0
kernel: Code: 25 28 00 00 00 75 29 c9 31 d2 31 c9 31 f6 31 ff 45 31 c0 45 31 c9 e9 5a 89 c7 00 48 89 fe 48 c7 c7 64 06 3f bd e8 1b 80 b4 ff <0f> 0b 31 c0 eb c7 e8 a0 ea c5 00 90 90 90 90 90 90 90 90 90 90 90
kernel: RSP: 0018:ffffacd857103cd0 EFLAGS: 00010246
kernel: RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
kernel: RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
kernel: RBP: ffffacd857103d20 R08: 0000000000000000 R09: 0000000000000000
kernel: R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000010000
kernel: R13: ffffffffc28e2ff8 R14: 0000000000000000 R15: 0000000000000001
kernel: FS: 0000000000000000(0000) GS:ffff918190080000(0000) knlGS:0000000000000000
kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
kernel: CR2: 00007835dca0b048 CR3: 00000003cb898000 CR4: 00000000003506f0
kernel: Call Trace:
kernel: <TASK>
kernel: ? show_regs+0x6d/0x80
kernel: ? __warn+0x89/0x160
kernel: ? sysfs_emit+0xb5/0xc0
kernel: ? report_bug+0x17e/0x1b0
kernel: ? handle_bug+0x51/0xa0
kernel: ? exc_invalid_op+0x18/0x80
kernel: ? asm_exc_invalid_op+0x1b/0x20
kernel: ? sysfs_emit+0xb5/0xc0
kernel: show_immediate+0x13f/0x1d0 [firewire_core]
kernel: init_fw_attribute_group+0x81/0x150 [firewire_core]
kernel: create_units+0x119/0x160 [firewire_core]
kernel: fw_device_init+0x1a9/0x330 [firewire_core]
kernel: fw_device_workfn+0x12/0x20 [firewire_core]
kernel: process_one_work+0x16f/0x350
kernel: worker_thread+0x306/0x440
kernel: ? __pfx_worker_thread+0x10/0x10
kernel: kthread+0xf2/0x120
kernel: ? __pfx_kthread+0x10/0x10
kernel: ret_from_fork+0x47/0x70
kernel: ? __pfx_kthread+0x10/0x10
kernel: ret_from_fork_asm+0x1b/0x30
kernel: </TASK>
kernel: ---[ end trace 0000000000000000 ]---
kernel: ------------[ cut here ]------------

Furthermore, 'show_text_leaf()' returns negative value when the NULL
pointer is passed. It results in the lack of vendor/model names from
sysfs.

I absolutely overlooked them. I would like to fix them within this merge
window, or revert them as a last resort...

Regards

Takashi Sakamoto