github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-07-27 17:47:41 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

ipv6: ndisc: fix NULL deref in accept_untracked_na()

Browse Source 
accept_untracked_na() re-fetches the inet6_dev with __in6_dev_get(dev)
and dereferences idev->cnf.accept_untracked_na without a NULL check,
even though its only caller ndisc_recv_na() already fetched and
NULL-checked idev for the same device.

Both reads of dev->ip6_ptr run in the same RCU read-side critical
section, but a concurrent addrconf_ifdown() can clear dev->ip6_ptr
between them: lowering the MTU below IPV6_MIN_MTU calls addrconf_ifdown()
without the synchronize_net() that orders the unregister path, so the
re-fetch returns NULL and oopses:

 BUG: KASAN: null-ptr-deref in ndisc_recv_na (net/ipv6/ndisc.c:974)
 Read of size 4 at addr 0000000000000364
 Call Trace:
  <IRQ>
  ndisc_recv_na (net/ipv6/ndisc.c:974)
  icmpv6_rcv (net/ipv6/icmp.c:1193)
  ip6_protocol_deliver_rcu (net/ipv6/ip6_input.c:479)
  ip6_input_finish (net/ipv6/ip6_input.c:534)
  ip6_input (net/ipv6/ip6_input.c:545)
  ip6_mc_input (net/ipv6/ip6_input.c:635)
  ipv6_rcv (net/ipv6/ip6_input.c:351)
  </IRQ>

It is reachable by an unprivileged user via a network namespace.

Pass the caller's already validated idev instead of re-fetching it; the
idev stays alive for the whole RCU critical section, so it is safe even
after dev->ip6_ptr has been cleared.

Fixes: aaa5f515b1 ("net: ipv6: new accept_untracked_na option to accept na only if in-network")
Reported-by: Xiang Mei <xmei5@asu.edu>
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
Reviewed-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Link: https://patch.msgid.link/20260617065512.2529757-2-bestswngs@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Weiming Shi 2026-06-17 14:55:13 +08:00 committed by Jakub Kicinski
parent 27ccb68e7c
commit d186e94236
1 changed files with 3 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
net/ipv6/ndisc.c
View File

@ -967,10 +967,8 @@ static enum skb_drop_reason ndisc_recv_ns(struct sk_buff *skb)
return reason;
}
static int accept_untracked_na(struct net_device *dev, struct in6_addr *saddr)
static int accept_untracked_na(struct inet6_dev *idev, struct in6_addr *saddr)
{
struct inet6_dev *idev = __in6_dev_get(dev);
switch (READ_ONCE(idev->cnf.accept_untracked_na)) {
case 0: /* Don't accept untracked na (absent in neighbor cache) */
return 0;
@ -980,7 +978,7 @@ static int accept_untracked_na(struct net_device *dev, struct in6_addr *saddr)
* same subnet as an address configured on the interface that
* received the na
*/
return !!ipv6_chk_prefix(saddr, dev);
return !!ipv6_chk_prefix(saddr, idev->dev);
default:
return 0;
}
@ -1078,7 +1076,7 @@ static enum skb_drop_reason ndisc_recv_na(struct sk_buff *skb)
*/
new_state = msg->icmph.icmp6_solicited ? NUD_REACHABLE : NUD_STALE;
if (!neigh && lladdr && idev && READ_ONCE(idev->cnf.forwarding)) {
if (accept_untracked_na(dev, saddr)) {
if (accept_untracked_na(idev, saddr)) {
neigh = neigh_create(&nd_tbl, &msg->target, dev);
new_state = NUD_STALE;
}