kernel/git/stable/linux-stable.git/net/ipv6, branch master

netfilter: handle unreadable frags

2026-07-08T13:33:44+00:00

sashiko reports: When an skb with unreadable fragments (such as from devmem TCP, where skb_frags_readable(skb) returns false) is processed by the u32 module, skb_copy_bits() will safely return a negative error code [..] xt_u32: bail out with hotdrop in this case. gather_frags: return -1, just as if we had no fragment header. nfnetlink_queue: restrict to the linear part. nfnetlink_log: restrict to the linear part. v2: - skb_zerocopy helpers don't copy readable flag, i.e. nfnetlink_queue is broken too xt_u32 shouldn't return true if hotdrop was set. Fixes: 65249feb6b3d ("net: add support for skbs with unreadable frags") Cc: stable@vger.kernel.org Acked-by: Mina Almasry Signed-off-by: Florian Westphal

netfilter: nf_conntrack_reasm: guard mac_header adjustment after IPv6 defrag

2026-07-08T13:22:03+00:00

nf_ct_frag6_reasm() slides the packet head forward to drop the IPv6 fragment header and then unconditionally advances skb->mac_header: skb->mac_header += sizeof(struct frag_hdr); On the NF_INET_LOCAL_OUT defrag path the skb has no link-layer header yet, so skb->mac_header is still the "not set" sentinel (u16)~0U. Adding sizeof(struct frag_hdr) wraps it to a small value (0xffff + 8 == 7), after which skb_mac_header_was_set() wrongly reports a MAC header is present and skb_mac_header() points into the headroom. The reassembler has done this unconditional add since it was introduced; it was harmless while mac_header was a bare pointer, but wrong once mac_header became a u16 offset whose unset state is the ~0U sentinel tested by skb_mac_header_was_set(). The sibling net/ipv6/reassembly.c does the same relocation and does guard the adjustment; mirror the guard here. Fixes: 9fb9cbb1082d ("[NETFILTER]: Add nf_conntrack subsystem.") Cc: stable@vger.kernel.org Reported-by: Weiming Shi Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Xiang Mei Signed-off-by: Florian Westphal

ipv6: mcast: Fix potential UAF in MLD delayed work

2026-07-08T12:41:01+00:00

A race condition exists between device teardown and incoming MLD query processing, leading to a Use-After-Free in the MLD delayed work. During device destruction, the primary reference to inet6_dev is dropped, which can drop its refcount to 0. The actual freeing of inet6_dev memory is deferred via RCU. Concurrently, the packet receive path runs under RCU read lock and obtains the inet6_dev pointer. Because the memory is RCU-protected, CPU-0 can safely dereference inet6_dev even if its refcount has hit 0. However, if CPU-0 calls igmp6_event_query() and schedules delayed work, it attempts to acquire a reference using in6_dev_hold(). This increments the refcount from 0 to 1, triggering a "refcount_t: addition on 0" warning. Since the inet6_dev memory is still scheduled to be freed after the RCU grace period, the device is freed while the work is still scheduled. When the work runs, it accesses the freed memory, causing a kernel panic. Fix this by using refcount_inc_not_zero() (via a new helper in6_dev_hold_safe()) to prevent acquiring a reference if the device is already being destroyed. If the refcount is 0, we do not schedule the work. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Eric Dumazet Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260705181756.963063-3-edumazet@google.com Signed-off-by: Paolo Abeni

netfilter: ip6tables: mark malformed IPv6 extension headers for hotdrop

2026-07-03T12:45:21+00:00

The ah, hbh and rt matches check that the fixed extension header is present, then use the header length field to derive the advertised extension header length for matching. For the ah match, add the missing advertised-length check. For hbh and rt, update the existing advertised-length checks. In all three cases, set hotdrop to true before returning false when the advertised extension header length exceeds the available skb data. Returning false treats the packet as a rule mismatch. Set hotdrop to true and drop malformed packets so they cannot bypass rules intended to drop packets with these IPv6 extension headers. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Zhixing Chen Signed-off-by: Florian Westphal

ipv6: fib6: fix NULL deref in fib6_walk_continue() on multi-batch dump

2026-06-30T01:28:41+00:00

inet6_dump_fib() saves its progress in cb->args[1] as a positional index within the current hash chain. Between batches, a concurrent fib6_new_table() can insert a new table at the chain head, shifting all existing entries. The saved index then lands on a different table, causing fib6_dump_table() to set w->root to the wrong table while w->node still points into the previous one. fib6_walk_continue() dereferences w->node->parent (NULL) and panics: BUG: kernel NULL pointer dereference, address: 0000000000000008 RIP: 0010:fib6_walk_continue+0x6e/0x170 Call Trace: fib6_dump_table.isra.0+0xc5/0x240 inet6_dump_fib+0xf6/0x420 rtnl_dumpit+0x30/0xa0 netlink_dump+0x15b/0x460 netlink_recvmsg+0x1d6/0x2a0 ____sys_recvmsg+0x17a/0x190 Fix by storing tb->tb6_id in cb->args[1] instead of a positional index. On resume, skip entries until the id matches; a concurrent head-insert can never match the saved id, so the walker always resumes on the correct table. Fixes: 1b43af5480c3 ("[IPV6]: Increase number of possible routing tables to 2^32") Signed-off-by: Pengfei Zhang Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260625070517.965597-1-zhangfeionline@gmail.com Signed-off-by: Jakub Kicinski

seg6: validate SRH length before reading fixed fields

2026-06-27T01:49:37+00:00

seg6_validate_srh() reads fixed SRH fields such as srh->type and srh->hdrlen before checking that the supplied length covers the fixed struct ipv6_sr_hdr fields. The BPF SEG6 encap path reaches this with a BPF program-supplied pointer and length: bpf_lwt_push_encap() and the SEG6 local BPF END_B6 and END_B6_ENCAP actions call bpf_push_seg6_encap(), which forwards the length to seg6_validate_srh() with no minimum-size guard. A 2-byte SEG6 encap header can therefore make the validator read srh->type at offset 2 beyond the caller-supplied buffer. Reject lengths shorter than the fixed SRH at the top of seg6_validate_srh(), before any field is read. This fixes the BPF helper path and keeps the common validator robust. Fixes: fe94cc290f53 ("bpf: Add IPv6 Segment Routing helpers") Signed-off-by: Nuoqi Gui Reviewed-by: Andrea Mayer Link: https://patch.msgid.link/20260623-f01-17-seg6-srh-len-v2-1-2edc40e9e3e1@mails.tsinghua.edu.cn Signed-off-by: Jakub Kicinski

ipv6: fix missing notification for ignore_routes_with_linkdown

2026-06-24T02:12:48+00:00

When changing the ignore_routes_with_linkdown sysctl for a specific interface, the RTM_NEWNETCONF netlink notification was not being emitted to userspace. Fix this by emitting the notification when needed. In addition, fix bogus return value for successful "all" and specific interface write operation leading to a wrong reset of the position pointer. Fixes: 35103d11173b ("net: ipv6 sysctl option to ignore routes when nexthop link is down") Reviewed-by: Nicolas Dichtel Signed-off-by: Fernando Fernandez Mancera Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260622130857.5115-7-fmancera@suse.de Signed-off-by: Jakub Kicinski

ipv6: fix state corruption during proxy_ndp sysctl restart

2026-06-24T02:12:47+00:00

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") Reviewed-by: Nicolas Dichtel Signed-off-by: Fernando Fernandez Mancera Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260622130857.5115-6-fmancera@suse.de Signed-off-by: Jakub Kicinski

ipv6: fix error handling in disable_policy sysctl

2026-06-24T02:12:47+00:00

When writing to the disable_policy sysctl, if proc_dointvec() fails to parse the input, it returns a negative error code. The current implementation is resetting the position argument even if an error occurred during proc_dointvec() and not only during sysctl restart. Fix this by checking the return value of proc_dointvec() and returning early on failure. Fixes: df789fe75206 ("ipv6: Provide ipv6 version of "disable_policy" sysctl") Reviewed-by: Nicolas Dichtel Signed-off-by: Fernando Fernandez Mancera Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260622130857.5115-5-fmancera@suse.de Signed-off-by: Jakub Kicinski

ipv6: fix error handling in forwarding sysctl

2026-06-24T02:12:47+00:00

When writing to the forwarding sysctl, if proc_dointvec() fails to parse the input, it returns a negative error code. The current implementation is overwriting that error for write operations. This results in a silent failure, it returns a successful write although the configuration was not modified at all. When modifying the "all" variant it can also modify the configuration of existing interfaces to the wrong value. Fix this by checking the return value of proc_dointvec() and returning early on failure. In addition, adjust return code of addrconf_fixup_forwarding() for successful operation. Fixes: b325fddb7f86 ("ipv6: Fix sysctl unregistration deadlock") Reviewed-by: Nicolas Dichtel Signed-off-by: Fernando Fernandez Mancera Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260622130857.5115-4-fmancera@suse.de Signed-off-by: Jakub Kicinski