[PATCH net v2 5/7] ipv6: reset value and position for proxy_ndp sysctl restart
From: Fernando Fernandez Mancera <hidden>
Date: 2026-06-20 16:19:24
Subsystem:
networking [general], networking [ipv4/ipv6], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, David Ahern, Ido Schimmel, Linus Torvalds
When handling proxy_ndp, if rtnl_net_trylock() fails, the operation is
retried but as the value was already modified by the initial
proc_dointvec() call, the restarted syscall will read the newly modified
value as the 'old' state.
Fix this by taking the RTNL lock before parsing the input value if the
operation is a write.
Fixes: c92d5491a6d9 ("netconf: add support for IPv6 proxy_ndp")
Signed-off-by: Fernando Fernandez Mancera <redacted>
---
net/ipv6/addrconf.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 5d96cbf76134..82b6f603faa0 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c@@ -6482,20 +6482,19 @@ static int addrconf_sysctl_disable(const struct ctl_table *ctl, int write, static int addrconf_sysctl_proxy_ndp(const struct ctl_table *ctl, int write, void *buffer, size_t *lenp, loff_t *ppos) { + struct net *net = ctl->extra2; int *valp = ctl->data; - int ret; int old, new; + int ret; + + if (write && !rtnl_net_trylock(net)) + return restart_syscall(); old = *valp; ret = proc_dointvec(ctl, write, buffer, lenp, ppos); new = *valp; if (write && old != new) { - struct net *net = ctl->extra2; - - if (!rtnl_net_trylock(net)) - return restart_syscall(); - if (valp == &net->ipv6.devconf_dflt->proxy_ndp) { inet6_netconf_notify_devconf(net, RTM_NEWNETCONF, NETCONFA_PROXY_NEIGH,
@@ -6514,8 +6513,9 @@ static int addrconf_sysctl_proxy_ndp(const struct ctl_table *ctl, int write, idev->dev->ifindex, &idev->cnf); } - rtnl_net_unlock(net); } + if (write) + rtnl_net_unlock(net); return ret; }
--
2.54.0