[PATCH OLK-6.6 0/2] net: Fix CVE-2026-45905 ip_rt_bug race in ICMP reverse path
From: Dong Chenchen <dongchenchen2@huawei.com> net: Fix CVE-2026-45905 ip_rt_bug race in ICMP reverse path This patch series fixes CVE-2026-45905 in the OLK-6.6 branch. * Patch 1: Switch icmp_route_lookup and ip_options_rcv_srr to use skb_dstref_steal/skb_dstref_restore helpers (dependency for CVE fix) * Patch 2: Fix ip_rt_bug race condition in icmp_route_lookup reverse path by checking rt2->rt_type after ip_route_input() for RTN_LOCAL Jiayuan Chen (1): xfrm: fix ip_rt_bug race in icmp_route_lookup reverse path Stanislav Fomichev (1): net: Switch to skb_dstref_steal/skb_dstref_restore for ip_route_input callers net/ipv4/icmp.c | 22 +++++++++++++++++++--- net/ipv4/ip_options.c | 5 ++--- 2 files changed, 21 insertions(+), 6 deletions(-) -- 2.43.0
From: Stanislav Fomichev <sdf@fomichev.me> stable inclusion from stable-v6.6.128 commit d621dd67a72d46a3f5329dbea8f8368228d4a3d7 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/14564 CVE: CVE-2026-45905 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit e97e6a1830ddb5885ba312e56b6fa3aa39b5f47e ] Going forward skb_dst_set will assert that skb dst_entry is empty during skb_dst_set. skb_dstref_steal is added to reset existing entry without doing refcnt. skb_dstref_restore should be used to restore the previous entry. Convert icmp_route_lookup and ip_options_rcv_srr to these helpers. Add extra call to skb_dstref_reset to icmp_route_lookup to clear the ip_route_input entry. Signed-off-by: Stanislav Fomichev <sdf@fomichev.me> Link: https://patch.msgid.link/20250818154032.3173645-5-sdf@fomichev.me Signed-off-by: Jakub Kicinski <kuba@kernel.org> Stable-dep-of: 81b84de32bb2 ("xfrm: fix ip_rt_bug race in icmp_route_lookup reverse path") Signed-off-by: Sasha Levin <sashal@kernel.org> Conflicts: net/ipv4/icmp.c net/ipv4/ip_options.c [commit 7e863e5db618 ("ipv4: Convert ip_route_input() to dscp_t") introduced dscp/ip4h_dscp() calls which are not present in OLK-6.6. Adapted to preserve OLK-6.6's RT_TOS(tos)/iph->tos patterns.] Signed-off-by: Dong Chenchen <dongchenchen2@huawei.com> --- net/ipv4/icmp.c | 7 ++++--- net/ipv4/ip_options.c | 5 ++--- 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c index 2745493d6b4f..c547490066a0 100644 --- a/net/ipv4/icmp.c +++ b/net/ipv4/icmp.c @@ -553,14 +553,15 @@ static struct rtable *icmp_route_lookup(struct net *net, goto relookup_failed; } /* Ugh! */ - orefdst = skb_in->_skb_refdst; /* save old refdst */ - skb_dst_set(skb_in, NULL); + orefdst = skb_dstref_steal(skb_in); err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr, RT_TOS(tos), rt2->dst.dev); dst_release(&rt2->dst); rt2 = skb_rtable(skb_in); - skb_in->_skb_refdst = orefdst; /* restore old refdst */ + /* steal dst entry from skb_in, don't drop refcnt */ + skb_dstref_steal(skb_in); + skb_dstref_restore(skb_in, orefdst); } if (err) diff --git a/net/ipv4/ip_options.c b/net/ipv4/ip_options.c index a9e22a098872..a84f095b99fc 100644 --- a/net/ipv4/ip_options.c +++ b/net/ipv4/ip_options.c @@ -615,13 +615,12 @@ int ip_options_rcv_srr(struct sk_buff *skb, struct net_device *dev) } memcpy(&nexthop, &optptr[srrptr-1], 4); - orefdst = skb->_skb_refdst; - skb_dst_set(skb, NULL); + orefdst = skb_dstref_steal(skb); err = ip_route_input(skb, nexthop, iph->saddr, iph->tos, dev); rt2 = skb_rtable(skb); if (err || (rt2->rt_type != RTN_UNICAST && rt2->rt_type != RTN_LOCAL)) { skb_dst_drop(skb); - skb->_skb_refdst = orefdst; + skb_dstref_restore(skb, orefdst); return -EINVAL; } refdst_drop(orefdst); -- 2.43.0
From: Jiayuan Chen <jiayuan.chen@shopee.com> [ Upstream commit 81b84de32bb27ae1ae2eb9acf0420e9d0d14bf00 ] icmp_route_lookup() performs multiple route lookups to find a suitable route for sending ICMP error messages, with special handling for XFRM (IPsec) policies. The lookup sequence is: 1. First, lookup output route for ICMP reply (dst = original src) 2. Pass through xfrm_lookup() for policy check 3. If blocked (-EPERM) or dst is not local, enter "reverse path" 4. In reverse path, call xfrm_decode_session_reverse() to get fl4_dec which reverses the original packet's flow (saddr<->daddr swapped) 5. If fl4_dec.saddr is local (we are the original destination), use __ip_route_output_key() for output route lookup 6. If fl4_dec.saddr is NOT local (we are a forwarding node), use ip_route_input() to simulate the reverse packet's input path 7. Finally, pass rt2 through xfrm_lookup() with XFRM_LOOKUP_ICMP flag The bug occurs in step 6: ip_route_input() is called with fl4_dec.daddr (original packet's source) as destination. If this address becomes local between the initial check and ip_route_input() call (e.g., due to concurrent "ip addr add"), ip_route_input() returns a LOCAL route with dst.output set to ip_rt_bug. This route is then used for ICMP output, causing dst_output() to call ip_rt_bug(), triggering a WARN_ON: ------------[ cut here ]------------ WARNING: net/ipv4/route.c:1275 at ip_rt_bug+0x21/0x30, CPU#1 Call Trace: <TASK> ip_push_pending_frames+0x202/0x240 icmp_push_reply+0x30d/0x430 __icmp_send+0x1149/0x24f0 ip_options_compile+0xa2/0xd0 ip_rcv_finish_core+0x829/0x1950 ip_rcv+0x2d7/0x420 __netif_receive_skb_one_core+0x185/0x1f0 netif_receive_skb+0x90/0x450 tun_get_user+0x3413/0x3fb0 tun_chr_write_iter+0xe4/0x220 ... Fix this by checking rt2->rt_type after ip_route_input(). If it's RTN_LOCAL, the route cannot be used for output, so treat it as an error. The reproducer requires kernel modification to widen the race window, making it unsuitable as a selftest. It is available at: https://gist.github.com/mrpre/eae853b72ac6a750f5d45d64ddac1e81 Reported-by: syzbot+e738404dcd14b620923c@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/000000000000b1060905eada8881@google.com/T/ Closes: https://lore.kernel.org/r/20260128090523.356953-1-jiayuan.chen@linux.dev Fixes: 8b7817f3a959 ("[IPSEC]: Add ICMP host relookup support") Signed-off-by: Jiayuan Chen <jiayuan.chen@shopee.com> Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev> Link: https://patch.msgid.link/20260206050220.59642-1-jiayuan.chen@linux.dev Signed-off-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Dong Chenchen <dongchenchen2@huawei.com> --- net/ipv4/icmp.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c index c547490066a0..e02937e8161a 100644 --- a/net/ipv4/icmp.c +++ b/net/ipv4/icmp.c @@ -562,6 +562,21 @@ static struct rtable *icmp_route_lookup(struct net *net, /* steal dst entry from skb_in, don't drop refcnt */ skb_dstref_steal(skb_in); skb_dstref_restore(skb_in, orefdst); + + /* + * At this point, fl4_dec.daddr should NOT be local (we + * checked fl4_dec.saddr above). However, a race condition + * may occur if the address is added to the interface + * concurrently. In that case, ip_route_input() returns a + * LOCAL route with dst.output=ip_rt_bug, which must not + * be used for output. + */ + if (!err && rt2 && rt2->rt_type == RTN_LOCAL) { + net_warn_ratelimited("detected local route for %pI4 during ICMP sending, src %pI4\n", + &fl4_dec.daddr, &fl4_dec.saddr); + dst_release(&rt2->dst); + err = -EINVAL; + } } if (err) -- 2.43.0
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