netdev - Re: [PATCH net v2 1/5] net/ipv6: fix addrconf_sysctl_addr_gen

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Date:   Mon, 9 Jul 2018 11:20:45 -0600
From:   David Ahern <dsahern@...il.com>
To:     Sabrina Dubroca <sd@...asysnail.net>, netdev@...r.kernel.org
Cc:     Jiri Pirko <jiri@...nulli.us>,
        Felix Jia <felix.jia@...iedtelesis.co.nz>
Subject: Re: [PATCH net v2 1/5] net/ipv6: fix addrconf_sysctl_addr_gen_mode

On 7/9/18 4:25 AM, Sabrina Dubroca wrote:
> addrconf_sysctl_addr_gen_mode() has multiple problems. First, it ignores
> the errors returned by proc_dointvec().
> 
> addrconf_sysctl_addr_gen_mode() calls proc_dointvec() directly, which
> writes the value to memory, and then checks if it's valid and may return
> EINVAL. If a bad value is given, the value displayed when reading
> net.ipv6.conf.foo.addr_gen_mode next time will be invalid. In case the
> value provided by the user was valid, addrconf_dev_config() won't be
> called since idev->cnf.addr_gen_mode has already been updated.
> 
> Fix this in the usual way we deal with values that need to be checked
> after the proc_do*() helper has returned: define a local ctl_table and
> storage, call proc_dointvec() on that temporary area, then check and
> store.
> 
> addrconf_sysctl_addr_gen_mode() also writes the new value to the global
> ipv6_devconf_dflt, when we're writing to some netns's default, so that
> new netns will inherit the value that was set by the change occuring in
> any netns. That doesn't make any sense, so let's drop this assignment.
> 
> Finally, since addr_gen_mode is a __u32, switch to proc_douintvec().
> 
> Fixes: d35a00b8e33d ("net/ipv6: allow sysctl to change link-local address generation mode")
> Signed-off-by: Sabrina Dubroca <sd@...asysnail.net>
> ---
>  net/ipv6/addrconf.c | 27 ++++++++++++++-------------
>  1 file changed, 14 insertions(+), 13 deletions(-)
> 

Reviewed-by: David Ahern <dsahern@...il.com>