linux.git/net/ipv6, branch v7.2-rc2

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

ipv6: fix error handling in ignore_routes_with_linkdown sysctl

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

When writing to the ignore_routes_with_linkdown 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.

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/20260622130857.5115-3-fmancera@suse.de
Signed-off-by: Jakub Kicinski

ipv6: fix error handling in disable_ipv6 sysctl

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

When writing to the disable_ipv6 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.

Fixes: 56d417b12e57 ("IPv6: Add 'autoconf' and 'disable_ipv6' module parameters")
Reviewed-by: Nicolas Dichtel 
Signed-off-by: Fernando Fernandez Mancera 
Reviewed-by: Ido Schimmel 
Link: https://patch.msgid.link/20260622130857.5115-2-fmancera@suse.de
Signed-off-by: Jakub Kicinski

Merge tag 'ipsec-2026-06-22' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec

2026-06-23T23:22:24+00:00

Steffen Klassert says:

====================
pull request (net): ipsec 2026-06-22

1) xfrm: use compat translator only for u64 alignment mismatch
   Gate the XFRM_USER_COMPAT translator on COMPAT_FOR_U64_ALIGNMENT
   so 32-bit compat tasks on arches whose 32-bit ABI already matches
   the native 64-bit layout are no longer rejected with -EOPNOTSUPP.
   From Sanman Pradhan.

2) net: af_key: initialize alg_key_len for IPComp states
   Initialize the alg_key_len to 0 in the IPComp branch of
   pfkey_msg2xfrm_state() so an uninitialized value cannot drive
   xfrm_alg_len() into a slab-out-of-bounds kmemdup during
   XFRM_MSG_MIGRATE. From Zijing Yin.

3) xfrm: Fix dev use-after-free in xfrm async resumption
   Stash the original skb->dev and extend the RCU critical section
   across xfrm_rcv_cb() and transport_finish() to prevent a
   tunnel-device UAF and original-device refcount leak when a
   callback replaces skb->dev. From Dong Chenchen.

4) xfrm: Fix xfrm state cache insertion race
   Move the state-validity check inside xfrm_state_lock in the
   input state cache insertion path so a state cannot be killed
   between the check and the insert. From Herbert Xu.

5) xfrm: annotate data-races around xfrm_policy_count[] and xfrm_policy_default[]
   Add READ_ONCE()/WRITE_ONCE() annotations on xfrm_policy_count
   and xfrm_policy_default to silence the KCSAN data race reported
   on net->xfrm.policy_count. From Eric Dumazet.

6) espintcp: use sk_msg_free_partial to fix partial send
   Replace the manual skmsg accounting in espintcp with
   sk_msg_free_partial() so the skmsg stays consistent on every
   iteration and the partial-send accounting bugs go away.
   From Sabrina Dubroca.

7) xfrm: validate selector family and prefixlen during match
   Reject mismatched address families in xfrm_selector_match() and
   bound prefixlen in addr4_match()/addr_match() to prevent the
   shift-out-of-bounds syzbot reported when an AF_UNSPEC selector
   with a large prefixlen is matched against an IPv4 flow.
   From Eric Dumazet.

* tag 'ipsec-2026-06-22' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec:
  xfrm: validate selector family and prefixlen during match
  espintcp: use sk_msg_free_partial to fix partial send
  xfrm: annotate data-races around xfrm_policy_count[] and xfrm_policy_default[]
  xfrm: Fix xfrm state cache insertion race
  xfrm: Fix dev use-after-free in xfrm async resumption
  net: af_key: initialize alg_key_len for IPComp states
  xfrm: use compat translator only for u64 alignment mismatch
====================

Link: https://patch.msgid.link/20260622075726.29685-1-steffen.klassert@secunet.com
Signed-off-by: Jakub Kicinski

ipv6: Fix null-ptr-deref in fib6_nh_mtu_change().

2026-06-23T01:20:09+00:00

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 
Signed-off-by: Xiang Mei 
Reviewed-by: Fernando Fernandez Mancera 
Reviewed-by: Ido Schimmel 
Link: https://patch.msgid.link/20260619045334.2427073-1-xmei5@asu.edu
Signed-off-by: Jakub Kicinski