diff options
| author | Breno Leitao <leitao@debian.org> | 2026-04-24 08:31:16 -0700 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-04-27 19:16:18 -0700 |
| commit | 3bc179bc7146c26c9dff75d2943d10528274e301 (patch) | |
| tree | e280e5e111a9e799cd727404c00696ec327b379f | |
| parent | 2b9f6f7065d4cfb65ba19126e0b35ac4544c3f3a (diff) | |
netpoll: fix IPv6 local-address corruption
netpoll_setup() decides whether to auto-populate the local source
address by testing np->local_ip.ip, which only inspects the first 4
bytes of the union inet_addr storage.
For an IPv6 netpoll whose caller-supplied local address has a zero
high-32 bits (::1, ::<suffix>, IPv4-mapped ::ffff:a.b.c.d, etc.), this
misdetects the address as unset (which they are not, but the first
4 bytes are empty), calls netpoll_take_ipv6() and overwrites it with
whatever matching link-local/global address the device happens to expose
first.
Introduce a helper netpoll_local_ip_unset() that picks the correct
family-aware test (ipv6_addr_any() for IPv6, !.ip for IPv4) and use it
from netpoll_setup().
Reproducer is something like:
echo "::2" > local_ip
echo 1 > enabled
cat local_ip
# before this fix: 2001:db8::1 (caller-supplied ::2 was clobbered)
# after this fix: ::2
Fixes: b7394d2429c1 ("netpoll: prepare for ipv6")
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20260424-netpoll_fix-v1-1-3a55348c625f@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | net/core/netpoll.c | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/net/core/netpoll.c b/net/core/netpoll.c index cd74beffd209..4381e0fc25bf 100644 --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -704,6 +704,23 @@ static int netpoll_take_ipv4(struct netpoll *np, struct net_device *ndev) return 0; } +/* + * Test whether the caller left np->local_ip unset, so that + * netpoll_setup() should auto-populate it from the egress device. + * + * np->local_ip is a union of __be32 (IPv4) and struct in6_addr (IPv6), + * so an IPv6 address whose first 4 bytes are zero (e.g. ::1, ::2, + * IPv4-mapped ::ffff:a.b.c.d) must not be tested via the IPv4 arm — + * doing so would misclassify a caller-supplied address as unset and + * silently overwrite it with whatever address the device exposes. + */ +static bool netpoll_local_ip_unset(const struct netpoll *np) +{ + if (np->ipv6) + return ipv6_addr_any(&np->local_ip.in6); + return !np->local_ip.ip; +} + int netpoll_setup(struct netpoll *np) { struct net *net = current->nsproxy->net_ns; @@ -747,7 +764,7 @@ int netpoll_setup(struct netpoll *np) rtnl_lock(); } - if (!np->local_ip.ip) { + if (netpoll_local_ip_unset(np)) { if (!np->ipv6) { err = netpoll_take_ipv4(np, ndev); if (err) |