Re: [PATCH] ipv6: delay procfs initialization after the ipv6 structs are ready

From: Shigeru Yoshida
Date: Wed Mar 20 2024 - 21:36:47 EST


On Wed, 20 Mar 2024 18:17:36 +0100, Nicolas Cavallari wrote:
> procfs files are created before the structure they reference are
> initialized. For example, if6_proc_init() creates procfs files that
> access structures initialized by addrconf_init().
>
> If ipv6 is compiled as a module and a program manages to open an ipv6
> procfs file during the loading of the module, it can oops the kernel.
>
> It appears that we were unlucky enough to reproduce this problem
> multiple times already, out of maybe 100 boots:
>
> NET: Registered PF_INET6 protocol family
> 8<--- cut here ---
> pwm-backlight backlight: supply power not found, using dummy regulator
> Segment Routing with IPv6
> In-situ OAM (IOAM) with IPv6
> Unable to handle kernel NULL pointer dereference at virtual address
> 00000000
> mt7915e 0000:03:00.0 wlp3s0: renamed from wlan0
> [00000000] *pgd=00000000
> Internal error: Oops: 5 [#1] SMP ARM
> Modules linked in: ipv6 mt7915e mt76_connac_lib mt76 dw_hdmi_imx
> mac80211 dw_hdmi drm_display_helper imxdrm drm_dma_helper
> drm_kms_helper snd_soc_imx_sgtl5000 syscopyarea sysfillrect sysimgblt
> fb_sys_fops imx_ipu_v3 snd_soc_fsl_asoc_card cfg80211 snd_soc_sgtl5000
> drm libarc4 snd_soc_fsl_ssi snd_soc_simple_card_utils imx_pcm_dma
> snd_soc_core rfkill snd_pcm_dmaengine snd_pcm
> drm_panel_orientation_quirks cfbfillrect cfbimgblt cfbcopyarea
> snd_timer snd egalax_ts snd_soc_imx_audmux soundcore flexcan mux_mmio
> imx2_wdt mux_core can_dev pwm_bl
> CPU: 2 PID: 850 Comm: snmpd Not tainted 6.1.14 #1
> Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
> PC is at if6_seq_start+0x2c/0x98 [ipv6]
> LR is at init_net+0x0/0xc00
> [...]
> if6_seq_start [ipv6] from seq_read_iter+0xb4/0x510
> seq_read_iter from seq_read+0x80/0xac
> seq_read from proc_reg_read+0xac/0x100
> proc_reg_read from vfs_read+0xb0/0x284
> vfs_read from ksys_read+0x64/0xec
> ksys_read from ret_fast_syscall+0x0/0x54
> Exception stack(0xf0e31fa8 to 0xf0e31ff0)
> 1fa0: b67fd0b0 be8a666b 0000000a b67fd148 00000400
> 00000000
> 1fc0: b67fd0b0 be8a666b 00000001 00000003 be8a67ec 00000000 b6d7e000
> b6c9954a
> 1fe0: b6d7eb30 be8a6638 b6ef11b4 b6ef0ddc
> Code: e5931004 e35100ff ca000014 e59e25dc (e7920101)
> ---[ end trace 0000000000000000 ]---
>
> Signed-off-by: Nicolas Cavallari <nicolas.cavallari@xxxxxxxxxxxxxxxxxxxxxxx>

The following tag is needed?

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")

Also, we should put appropriate prefix in the subject for netdev
patches, i.e. "net" or "net-next". As for this patch, I think
appropriate prefix is "[PATCH net]".

Anyway,

Reviewed-by: Shigeru Yoshida <syoshida@xxxxxxxxxx>

Thanks,
Shigeru