netdev - Re: [PATCH net v2] net-sysfs: check device is present when showing duplex

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Message-ID: <35c918f6-1919-4597-9113-398d5c633cc8@redhat.com>
Date: Tue, 30 Jul 2024 11:06:36 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Jamie Bainbridge <jamie.bainbridge@...il.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, David Decotigny <decot@...gle.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 Shigeru Yoshida <syoshida@...hat.com>,
 Johannes Berg <johannes@...solutions.net>
Subject: Re: [PATCH net v2] net-sysfs: check device is present when showing
 duplex

Hi,

On 7/29/24 02:12, Jamie Bainbridge wrote:
> A sysfs reader can race with a device reset or removal, attempting to
> read device state when the device is not actuall present.
> 
> This is the same sort of panic as observed in commit 4224cfd7fb65
> ("net-sysfs: add check for netdevice being present to speed_show"):
> 
>       [exception RIP: qed_get_current_link+17]
>    #8 [ffffb9e4f2907c48] qede_get_link_ksettings at ffffffffc07a994a [qede]
>    #9 [ffffb9e4f2907cd8] __rh_call_get_link_ksettings at ffffffff992b01a3
>   #10 [ffffb9e4f2907d38] __ethtool_get_link_ksettings at ffffffff992b04e4
>   #11 [ffffb9e4f2907d90] duplex_show at ffffffff99260300
>   #12 [ffffb9e4f2907e38] dev_attr_show at ffffffff9905a01c
>   #13 [ffffb9e4f2907e50] sysfs_kf_seq_show at ffffffff98e0145b
>   #14 [ffffb9e4f2907e68] seq_read at ffffffff98d902e3
>   #15 [ffffb9e4f2907ec8] vfs_read at ffffffff98d657d1
>   #16 [ffffb9e4f2907f00] ksys_read at ffffffff98d65c3f
>   #17 [ffffb9e4f2907f38] do_syscall_64 at ffffffff98a052fb
> 
>   crash> struct net_device.state ffff9a9d21336000
>     state = 5,
> 
> state 5 is __LINK_STATE_START (0b1) and __LINK_STATE_NOCARRIER (0b100).
> The device is not present, note lack of __LINK_STATE_PRESENT (0b10).
> 
> Resolve by adding the same netif_device_present() check to duplex_show.
> 
> Fixes: 8ae6daca85c8 ("ethtool: Call ethtool's get/set_settings callbacks with cleaned data")

the patch LGTM, but it looks like the issue pre-exist WRT the above 
blamed commit??! possibly:

Fixes: d519e17e2d01 ("net: export device speed and duplex via sysfs")

Also please explicitly CC people who gave feedback on previous revisions,

Thanks,

Paolo