diff options
| author | Xiang Mei <xmei5@asu.edu> | 2026-06-18 21:53:34 -0700 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-06-22 18:20:09 -0700 |
| commit | 46c3b8191aad3d032776bf3bebf03efdf5f4b905 (patch) | |
| tree | 63a74ca4636b9004a136ee1f01321de0bc6e613a | |
| parent | c78a4e41ab5ead6193ad8a2dd92e8906bae659fa (diff) | |
ipv6: Fix null-ptr-deref in fib6_nh_mtu_change().
fib6_nh_mtu_change() re-fetches idev via __in6_dev_get(arg->dev) and
dereferences idev->cnf.mtu6 without a NULL check. addrconf_ifdown()
clears dev->ip6_ptr with RCU_INIT_POINTER() after rt6_disable_ip() has
released tb6_lock, so the RA-driven MTU walk can observe a NULL idev and
oops. The caller rt6_mtu_change_route() guards its own __in6_dev_get(),
but this re-fetch is unguarded; nexthop-backed routes survive
addrconf_ifdown()'s flush, so the walk still reaches it after ip6_ptr is
nulled.
Return 0 when idev is NULL, matching rt6_mtu_change_route() and the
fib6_mtu() fix in commit 5ad509c1fdad ("ipv6: Fix null-ptr-deref in
fib6_mtu().").
Oops: general protection fault, ... KASAN: null-ptr-deref in range
[0x00000000000002a8-0x00000000000002af]
RIP: 0010:fib6_nh_mtu_change+0x203/0x990
rt6_mtu_change_route+0x141/0x1d0
__fib6_clean_all+0xd0/0x160
rt6_mtu_change+0xb4/0x100
ndisc_router_discovery+0x24b5/0x2cb0
icmpv6_rcv+0x12e9/0x1710
ipv6_rcv+0x39b/0x410
Fixes: c0b220cf7d80 ("ipv6: Refactor exception functions")
Reported-by: Weiming Shi <bestswngs@gmail.com>
Signed-off-by: Xiang Mei <xmei5@asu.edu>
Reviewed-by: Fernando Fernandez Mancera <fmancera@suse.de>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20260619045334.2427073-1-xmei5@asu.edu
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | net/ipv6/route.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 6361ad2fcf77..a1301334da48 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -5055,6 +5055,9 @@ static int fib6_nh_mtu_change(struct fib6_nh *nh, void *_arg) struct inet6_dev *idev = __in6_dev_get(arg->dev); u32 mtu = f6i->fib6_pmtu; + if (!idev) + return 0; + if (mtu >= arg->mtu || (mtu < arg->mtu && mtu == idev->cnf.mtu6)) fib6_metric_set(f6i, RTAX_MTU, arg->mtu); |