ipv6: fix error handling in disable_ipv6 sysctl

When writing to the disable_ipv6 sysctl, if proc_dointvec() fails to
parse the input, it returns a negative error code. The current
implementation is overwriting that error for write operations.

This results in a silent failure, it returns a successful write although
the configuration was not modified at all. When modifying the "all"
variant it can also modify the configuration of existing interfaces to
the wrong value.

Fix this by checking the return value of proc_dointvec() and returning
early on failure.

Fixes: 56d417b12e57 ("IPv6: Add 'autoconf' and 'disable_ipv6' module parameters")
Reviewed-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20260622130857.5115-2-fmancera@suse.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 1f21ccb55caa50c68e2010ff2489edc80257c884..c901b444a995e5fb98545498b0b917bf03eeacf8 100644 (file)
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -6467,6 +6467,8 @@ static int addrconf_sysctl_disable(const struct ctl_table *ctl, int write,
        lctl.data = &val;
 
        ret = proc_dointvec(&lctl, write, buffer, lenp, ppos);
+       if (ret)
+               return ret;
 
        if (write)
                ret = addrconf_disable_ipv6(ctl, valp, val);