netdev - Re: [PATCH] net: check all name nodes in __dev_alloc

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Date:   Thu, 18 Mar 2021 08:43:42 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Jiri Bohac <jbohac@...e.cz>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        Jiri Pirko <jiri@...dia.com>
Subject: Re: [PATCH] net: check all name nodes in  __dev_alloc_name

Thu, Mar 18, 2021 at 04:42:53AM CET, jbohac@...e.cz wrote:
>__dev_alloc_name(), when supplied with a name containing '%d',
>will search for the first available device number to generate a
>unique device name.
>
>Since commit ff92741270bf8b6e78aa885f166b68c7a67ab13a ("net:
>introduce name_node struct to be used in hashlist") network
>devices may have alternate names.  __dev_alloc_name() does take
>these alternate names into account, possibly generating a name
>that is already taken and failing with -ENFILE as a result.
>
>This demonstrates the bug:
>
>    # rmmod dummy 2>/dev/null
>    # ip link property add dev lo altname dummy0
>    # modprobe dummy numdummies=1
>    modprobe: ERROR: could not insert 'dummy': Too many open files in system
>
>Instead of creating a device named dummy1, modprobe fails.
>
>Fix this by checking all the names in the d->name_node list, not just d->name.
>
>Signed-off-by: Jiri Bohac <jbohac@...e.cz>
>Fixes: ff92741270bf ("net: introduce name_node struct to be used in hashlist")

Reviewed-by: Jiri Pirko <jiri@...dia.com>

Thanks!