kernel.git/net/ipv6/ip6_fib.c, branch linux-6.18.y

ipv6: Fix out-of-bound access in fib6_add_rt2node().

2026-02-26T22:59:38Z

[ Upstream commit 8244f959e2c125c849e569f5b23ed49804cce695 ] syzbot reported out-of-bound read in fib6_add_rt2node(). [0] When IPv6 route is created with RTA_NH_ID, struct fib6_info does not have the trailing struct fib6_nh. The cited commit started to check !iter->fib6_nh->fib_nh_gw_family to ensure that rt6_qualify_for_ecmp() will return false for iter. If iter->nh is not NULL, rt6_qualify_for_ecmp() returns false anyway. Let's check iter->nh before reading iter->fib6_nh and avoid OOB read. [0]: BUG: KASAN: slab-out-of-bounds in fib6_add_rt2node+0x349c/0x3500 net/ipv6/ip6_fib.c:1142 Read of size 1 at addr ffff8880384ba6de by task syz.0.18/5500 CPU: 0 UID: 0 PID: 5500 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xba/0x230 mm/kasan/report.c:482 kasan_report+0x117/0x150 mm/kasan/report.c:595 fib6_add_rt2node+0x349c/0x3500 net/ipv6/ip6_fib.c:1142 fib6_add_rt2node_nh net/ipv6/ip6_fib.c:1363 [inline] fib6_add+0x910/0x18c0 net/ipv6/ip6_fib.c:1531 __ip6_ins_rt net/ipv6/route.c:1351 [inline] ip6_route_add+0xde/0x1b0 net/ipv6/route.c:3957 inet6_rtm_newroute+0x268/0x19e0 net/ipv6/route.c:5660 rtnetlink_rcv_msg+0x7d5/0xbe0 net/core/rtnetlink.c:6958 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg net/socket.c:742 [inline] ____sys_sendmsg+0xa68/0xad0 net/socket.c:2592 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2646 __sys_sendmsg net/socket.c:2678 [inline] __do_sys_sendmsg net/socket.c:2683 [inline] __se_sys_sendmsg net/socket.c:2681 [inline] __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2681 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f9316b9aeb9 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffd8809b678 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f9316e15fa0 RCX: 00007f9316b9aeb9 RDX: 0000000000000000 RSI: 0000200000004380 RDI: 0000000000000003 RBP: 00007f9316c08c1f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f9316e15fac R14: 00007f9316e15fa0 R15: 00007f9316e15fa0 Allocated by task 5499: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 poison_kmalloc_redzone mm/kasan/common.c:398 [inline] __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415 kasan_kmalloc include/linux/kasan.h:263 [inline] __do_kmalloc_node mm/slub.c:5657 [inline] __kmalloc_noprof+0x40c/0x7e0 mm/slub.c:5669 kmalloc_noprof include/linux/slab.h:961 [inline] kzalloc_noprof include/linux/slab.h:1094 [inline] fib6_info_alloc+0x30/0xf0 net/ipv6/ip6_fib.c:155 ip6_route_info_create+0x142/0x860 net/ipv6/route.c:3820 ip6_route_add+0x49/0x1b0 net/ipv6/route.c:3949 inet6_rtm_newroute+0x268/0x19e0 net/ipv6/route.c:5660 rtnetlink_rcv_msg+0x7d5/0xbe0 net/core/rtnetlink.c:6958 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg net/socket.c:742 [inline] ____sys_sendmsg+0xa68/0xad0 net/socket.c:2592 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2646 __sys_sendmsg net/socket.c:2678 [inline] __do_sys_sendmsg net/socket.c:2683 [inline] __se_sys_sendmsg net/socket.c:2681 [inline] __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2681 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Fixes: bbf4a17ad9ff ("ipv6: Fix ECMP sibling count mismatch when clearing RTF_ADDRCONF") Reported-by: syzbot+707d6a5da1ab9e0c6f9d@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/698cbfba.050a0220.2eeac1.009d.GAE@google.com/ Signed-off-by: Kuniyuki Iwashima Reviewed-by: Fernando Fernandez Mancera Reviewed-by: Shigeru Yoshida Link: https://patch.msgid.link/20260211175133.3657034-1-kuniyu@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

ipv6: Fix ECMP sibling count mismatch when clearing RTF_ADDRCONF

2026-02-11T12:41:59Z

[ Upstream commit bbf4a17ad9ffc4e3d7ec13d73ecd59dea149ed25 ] syzbot reported a kernel BUG in fib6_add_rt2node() when adding an IPv6 route. [0] Commit f72514b3c569 ("ipv6: clear RA flags when adding a static route") introduced logic to clear RTF_ADDRCONF from existing routes when a static route with the same nexthop is added. However, this causes a problem when the existing route has a gateway. When RTF_ADDRCONF is cleared from a route that has a gateway, that route becomes eligible for ECMP, i.e. rt6_qualify_for_ecmp() returns true. The issue is that this route was never added to the fib6_siblings list. This leads to a mismatch between the following counts: - The sibling count computed by iterating fib6_next chain, which includes the newly ECMP-eligible route - The actual siblings in fib6_siblings list, which does not include that route When a subsequent ECMP route is added, fib6_add_rt2node() hits BUG_ON(sibling->fib6_nsiblings != rt->fib6_nsiblings) because the counts don't match. Fix this by only clearing RTF_ADDRCONF when the existing route does not have a gateway. Routes without a gateway cannot qualify for ECMP anyway (rt6_qualify_for_ecmp() requires fib_nh_gw_family), so clearing RTF_ADDRCONF on them is safe and matches the original intent of the commit. [0]: kernel BUG at net/ipv6/ip6_fib.c:1217! Oops: invalid opcode: 0000 [#1] SMP KASAN PTI CPU: 0 UID: 0 PID: 6010 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 RIP: 0010:fib6_add_rt2node+0x3433/0x3470 net/ipv6/ip6_fib.c:1217 [...] Call Trace: fib6_add+0x8da/0x18a0 net/ipv6/ip6_fib.c:1532 __ip6_ins_rt net/ipv6/route.c:1351 [inline] ip6_route_add+0xde/0x1b0 net/ipv6/route.c:3946 ipv6_route_ioctl+0x35c/0x480 net/ipv6/route.c:4571 inet6_ioctl+0x219/0x280 net/ipv6/af_inet6.c:577 sock_do_ioctl+0xdc/0x300 net/socket.c:1245 sock_ioctl+0x576/0x790 net/socket.c:1366 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Fixes: f72514b3c569 ("ipv6: clear RA flags when adding a static route") Reported-by: syzbot+cb809def1baaac68ab92@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=cb809def1baaac68ab92 Tested-by: syzbot+cb809def1baaac68ab92@syzkaller.appspotmail.com Signed-off-by: Shigeru Yoshida Reviewed-by: Fernando Fernandez Mancera Link: https://patch.msgid.link/20260204095837.1285552-1-syoshida@redhat.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

ipv6: clear RA flags when adding a static route

2025-12-18T13:03:05Z

[ Upstream commit f72514b3c5698e4b900b25345e09f9ed33123de6 ] When an IPv6 Router Advertisement (RA) is received for a prefix, the kernel creates the corresponding on-link route with flags RTF_ADDRCONF and RTF_PREFIX_RT configured and RTF_EXPIRES if lifetime is set. If later a user configures a static IPv6 address on the same prefix the kernel clears the RTF_EXPIRES flag but it doesn't clear the RTF_ADDRCONF and RTF_PREFIX_RT. When the next RA for that prefix is received, the kernel sees the route as RA-learned and wrongly configures back the lifetime. This is problematic because if the route expires, the static address won't have the corresponding on-link route. This fix clears the RTF_ADDRCONF and RTF_PREFIX_RT flags preventing that the lifetime is configured when the next RA arrives. If the static address is deleted, the route becomes RA-learned again. Fixes: 14ef37b6d00e ("ipv6: fix route lookup in addrconf_prefix_rcv()") Reported-by: Garri Djavadyan Closes: https://lore.kernel.org/netdev/ba807d39aca5b4dcf395cc11dca61a130a52cfd3.camel@gmail.com/ Signed-off-by: Fernando Fernandez Mancera Reviewed-by: David Ahern Link: https://patch.msgid.link/20251115095939.6967-1-fmancera@suse.de Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2025-07-26T18:49:45Z

Merge in late fixes to prepare for the 6.17 net-next PR. Conflicts: net/core/neighbour.c 1bbb76a89948 ("neighbour: Fix null-ptr-deref in neigh_flush_dev().") 13a936bb99fb ("neighbour: Protect tbl->phash_buckets[] with a dedicated mutex.") 03dc03fa0432 ("neighbor: Add NTF_EXT_VALIDATED flag for externally validated entries") Adjacent changes: drivers/net/usb/usbnet.c 0d9cfc9b8cb1 ("net: usbnet: Avoid potential RCU stall on LINK_CHANGE event") 2c04d279e857 ("net: usb: Convert tasklet API to new bottom half workqueue mechanism") net/ipv6/route.c 31d7d67ba127 ("ipv6: annotate data-races around rt->fib6_nsiblings") 1caf27297215 ("ipv6: adopt dst_dev() helper") 3b3ccf9ed05e ("net: Remove unnecessary NULL check for lwtunnel_fill_encap()") Signed-off-by: Jakub Kicinski

ipv6: annotate data-races around rt->fib6_nsiblings

2025-07-26T18:31:00Z

rt->fib6_nsiblings can be read locklessly, add corresponding READ_ONCE() and WRITE_ONCE() annotations. Fixes: 66f5d6ce53e6 ("ipv6: replace rwlock with rcu and spinlock in fib6_table") Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20250725140725.3626540-5-edumazet@google.com Signed-off-by: Jakub Kicinski

ipv6: prevent infinite loop in rt6_nlmsg_size()

2025-07-26T18:31:00Z

While testing prior patch, I was able to trigger an infinite loop in rt6_nlmsg_size() in the following place: list_for_each_entry_rcu(sibling, &f6i->fib6_siblings, fib6_siblings) { rt6_nh_nlmsg_size(sibling->fib6_nh, &nexthop_len); } This is because fib6_del_route() and fib6_add_rt2node() uses list_del_rcu(), which can confuse rcu readers, because they might no longer see the head of the list. Restart the loop if f6i->fib6_nsiblings is zero. Fixes: d9ccb18f83ea ("ipv6: Fix soft lockups in fib6_select_path under high next hop churn") Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20250725140725.3626540-3-edumazet@google.com Signed-off-by: Jakub Kicinski

ipv6: Cleanup fib6_drop_pcpu_from()

2025-07-03T14:00:50Z

Since commit 0e2338749192 ("ipv6: fix races in ip6_dst_destroy()"), 'table' is unused in __fib6_drop_pcpu_from(), no need pass it from fib6_drop_pcpu_from(). Signed-off-by: Yue Haibing Reviewed-by: Simon Horman Link: https://patch.msgid.link/20250701041235.1333687-1-yuehaibing@huawei.com Signed-off-by: Paolo Abeni

treewide, timers: Rename from_timer() to timer_container_of()

2025-06-08T07:07:37Z

Move this API to the canonical timer_*() namespace. [ tglx: Redone against pre rc1 ] Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/aB2X0jCKQO56WdMt@gmail.com

ipv6: Narrow down RCU critical section in inet6_rtm_newroute().

2025-05-21T02:18:24Z

Commit 169fd62799e8 ("ipv6: Get rid of RTNL for SIOCADDRT and RTM_NEWROUTE.") added rcu_read_lock() covering ip6_route_info_create_nh() and __ip6_ins_rt() to guarantee that nexthop and netdev will not go away. However, as reported by syzkaller [0], ip_tun_build_state() calls dst_cache_init() with GFP_KERNEL during the RCU critical section. ip6_route_info_create_nh() fetches nexthop or netdev depending on whether RTA_NH_ID is set, and struct fib6_info holds a refcount of either of them by nexthop_get() or netdev_get_by_index(). netdev_get_by_index() looks up a dev and calls dev_hold() under RCU. So, we need RCU only around nexthop_find_by_id() and nexthop_get() ( and a few more nexthop code). Let's add rcu_read_lock() there and remove rcu_read_lock() in ip6_route_add() and ip6_route_multipath_add(). Now these functions called from fib6_add() need RCU: - inet6_rt_notify() - fib6_drop_pcpu_from() (via fib6_purge_rt()) - rt6_flush_exceptions() (via fib6_purge_rt()) - ip6_ignore_linkdown() (via rt6_multipath_rebalance()) All callers of inet6_rt_notify() need RCU, so rcu_read_lock() is added there. [0]: [ BUG: Invalid wait context ] 6.15.0-rc4-syzkaller-00746-g836b313a14a3 #0 Tainted: G W ---------------------------- syz-executor234/5832 is trying to lock: ffffffff8e021688 (pcpu_alloc_mutex){+.+.}-{4:4}, at: pcpu_alloc_noprof+0x284/0x16b0 mm/percpu.c:1782 other info that might help us debug this: context-{5:5} 1 lock held by syz-executor234/5832: 0: ffffffff8df3b860 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] 0: ffffffff8df3b860 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] 0: ffffffff8df3b860 (rcu_read_lock){....}-{1:3}, at: ip6_route_add+0x4d/0x2f0 net/ipv6/route.c:3913 stack backtrace: CPU: 0 UID: 0 PID: 5832 Comm: syz-executor234 Tainted: G W 6.15.0-rc4-syzkaller-00746-g836b313a14a3 #0 PREEMPT(full) Tainted: [W]=WARN Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/29/2025 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_lock_invalid_wait_context kernel/locking/lockdep.c:4831 [inline] check_wait_context kernel/locking/lockdep.c:4903 [inline] __lock_acquire+0xbcf/0xd20 kernel/locking/lockdep.c:5185 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866 __mutex_lock_common kernel/locking/mutex.c:601 [inline] __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746 pcpu_alloc_noprof+0x284/0x16b0 mm/percpu.c:1782 dst_cache_init+0x37/0xc0 net/core/dst_cache.c:145 ip_tun_build_state+0x193/0x6b0 net/ipv4/ip_tunnel_core.c:687 lwtunnel_build_state+0x381/0x4c0 net/core/lwtunnel.c:137 fib_nh_common_init+0x129/0x460 net/ipv4/fib_semantics.c:635 fib6_nh_init+0x15e4/0x2030 net/ipv6/route.c:3669 ip6_route_info_create_nh+0x139/0x870 net/ipv6/route.c:3866 ip6_route_add+0xf6/0x2f0 net/ipv6/route.c:3915 inet6_rtm_newroute+0x284/0x1c50 net/ipv6/route.c:5732 rtnetlink_rcv_msg+0x7cc/0xb70 net/core/rtnetlink.c:6955 netlink_rcv_skb+0x219/0x490 net/netlink/af_netlink.c:2534 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline] netlink_unicast+0x758/0x8d0 net/netlink/af_netlink.c:1339 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1883 sock_sendmsg_nosec net/socket.c:712 [inline] __sock_sendmsg+0x219/0x270 net/socket.c:727 ____sys_sendmsg+0x505/0x830 net/socket.c:2566 ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2620 __sys_sendmsg net/socket.c:2652 [inline] __do_sys_sendmsg net/socket.c:2657 [inline] __se_sys_sendmsg net/socket.c:2655 [inline] __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2655 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94 Fixes: 169fd62799e8 ("ipv6: Get rid of RTNL for SIOCADDRT and RTM_NEWROUTE.") Reported-by: syzbot+bcc12d6799364500fbec@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=bcc12d6799364500fbec Reported-by: Eric Dumazet Closes: https://lore.kernel.org/netdev/CANn89i+r1cGacVC_6n3-A-WSkAa_Nr+pmxJ7Gt+oP-P9by2aGw@mail.gmail.com/ Signed-off-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250516022759.44392-4-kuniyu@amazon.com Signed-off-by: Jakub Kicinski

ipv6: Remove rcu_read_lock() in fib6_get_table().

2025-05-21T02:18:23Z

Once allocated, the IPv6 routing table is not freed until netns is dismantled. fib6_get_table() uses rcu_read_lock() while iterating net->ipv6.fib_table_hash[], but it's not needed and rather confusing. Because some callers have this pattern, table = fib6_get_table(); rcu_read_lock(); /* ... use table here ... */ rcu_read_unlock(); [ See: addrconf_get_prefix_route(), ip6_route_del(), rt6_get_route_info(), rt6_get_dflt_router() ] and this looks illegal but is actually safe. Let's remove rcu_read_lock() in fib6_get_table() and pass true to the last argument of hlist_for_each_entry_rcu() to bypass the RCU check. Note that protection is not needed but RCU helper is used to avoid data-race. Signed-off-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250516022759.44392-2-kuniyu@amazon.com Signed-off-by: Jakub Kicinski