kernel/net/ipv6/ip6_output.c, branch linux-5.10.y

ipv6: Fix potential uninit-value access in __ip6_make_skb()

2026-01-19T12:12:01Z

commit 4e13d3a9c25b7080f8a619f961e943fe08c2672c upstream. As it was done in commit fc1092f51567 ("ipv4: Fix uninit-value access in __ip_make_skb()") for IPv4, check FLOWI_FLAG_KNOWN_NH on fl6->flowi6_flags instead of testing HDRINCL on the socket to avoid a race condition which causes uninit-value access. Fixes: ea30388baebc ("ipv6: Fix an uninit variable access bug in __ip6_make_skb()") Signed-off-by: Shigeru Yoshida Signed-off-by: David S. Miller [ Referred stable v6.1.y version of the patch to generate this one v6.1 link: https://github.com/gregkh/linux/commit/a05c1ede50e9656f0752e523c7b54f3a3489e9a8 ] Signed-off-by: Shubham Kulkarni Signed-off-by: Greg Kroah-Hartman

Revert "ipv6: save dontfrag in cork"

2025-07-17T16:27:44Z

This reverts commit 29533d1a54b8de5aaf8c4aa6790dc67d5c14fba5 which is commit a18dfa9925b9ef6107ea3aa5814ca3c704d34a8a upstream. A regression was introduced when backporting this to the stable kernels without applying previous commits in this series. When sending IPv6 UDP packets larger than MTU, EMSGSIZE was returned instead of fragmenting the packets as expected. As there is no compelling reason for this commit to be present in the stable kernels it should be reverted. Signed-off-by: Brett A C Sheffield Signed-off-by: Greg Kroah-Hartman

ipv6: save dontfrag in cork

2025-06-04T12:37:01Z

[ Upstream commit a18dfa9925b9ef6107ea3aa5814ca3c704d34a8a ] When spanning datagram construction over multiple send calls using MSG_MORE, per datagram settings are configured on the first send. That is when ip(6)_setup_cork stores these settings for subsequent use in __ip(6)_append_data and others. The only flag that escaped this was dontfrag. As a result, a datagram could be constructed with df=0 on the first sendmsg, but df=1 on a next. Which is what cmsg_ip.sh does in an upcoming MSG_MORE test in the "diff" scenario. Changing datagram conditions in the middle of constructing an skb makes this already complex code path even more convoluted. It is here unintentional. Bring this flag in line with expected sockopt/cmsg behavior. And stop passing ipc6 to __ip6_append_data, to avoid such issues in the future. This is already the case for __ip_append_data. inet6_cork had a 6 byte hole, so the 1B flag has no impact. Signed-off-by: Willem de Bruijn Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20250307033620.411611-3-willemdebruijn.kernel@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

ipv6: Fix signed integer overflow in __ip6_append_data

2025-04-10T12:30:48Z

commit f93431c86b631bbca5614c66f966bf3ddb3c2803 upstream. Resurrect ubsan overflow checks and ubsan report this warning, fix it by change the variable [length] type to size_t. UBSAN: signed-integer-overflow in net/ipv6/ip6_output.c:1489:19 2147479552 + 8567 cannot be represented in type 'int' CPU: 0 PID: 253 Comm: err Not tainted 5.16.0+ #1 Hardware name: linux,dummy-virt (DT) Call trace: dump_backtrace+0x214/0x230 show_stack+0x30/0x78 dump_stack_lvl+0xf8/0x118 dump_stack+0x18/0x30 ubsan_epilogue+0x18/0x60 handle_overflow+0xd0/0xf0 __ubsan_handle_add_overflow+0x34/0x44 __ip6_append_data.isra.48+0x1598/0x1688 ip6_append_data+0x128/0x260 udpv6_sendmsg+0x680/0xdd0 inet6_sendmsg+0x54/0x90 sock_sendmsg+0x70/0x88 ____sys_sendmsg+0xe8/0x368 ___sys_sendmsg+0x98/0xe0 __sys_sendmmsg+0xf4/0x3b8 __arm64_sys_sendmmsg+0x34/0x48 invoke_syscall+0x64/0x160 el0_svc_common.constprop.4+0x124/0x300 do_el0_svc+0x44/0xc8 el0_svc+0x3c/0x1e8 el0t_64_sync_handler+0x88/0xb0 el0t_64_sync+0x16c/0x170 Changes since v1: -Change the variable [length] type to unsigned, as Eric Dumazet suggested. Changes since v2: -Don't change exthdrlen type in ip6_make_skb, as Paolo Abeni suggested. Changes since v3: -Don't change ulen type in udpv6_sendmsg and l2tp_ip6_sendmsg, as Jakub Kicinski suggested. Reported-by: Hulk Robot Signed-off-by: Wang Yufen Link: https://lore.kernel.org/r/20220607120028.845916-1-wangyufen@huawei.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin [ Conflict due to f37a4cc6bb0b ("udp6: pass flow in ip6_make_skb together with cork") not in the tree ] Signed-off-by: Abdelkareem Abdelsaamad Signed-off-by: Greg Kroah-Hartman

net: use indirect call helpers for dst_output

2025-03-13T11:47:32Z

[ Upstream commit 6585d7dc491d9d5e323ed52ee32ad071e04c9dfa ] This patch avoids the indirect call for the common case: ip6_output and ip_output Signed-off-by: Brian Vazquez Signed-off-by: Jakub Kicinski Stable-dep-of: 13e55fbaec17 ("net: ipv6: fix dst ref loop on input in rpl lwt") Signed-off-by: Sasha Levin

ipv6: prevent possible UAF in ip6_xmit()

2025-01-09T12:25:00Z

commit 2d5ff7e339d04622d8282661df36151906d0e1c7 upstream. If skb_expand_head() returns NULL, skb has been freed and the associated dst/idev could also have been freed. We must use rcu_read_lock() to prevent a possible UAF. Fixes: 0c9f227bee11 ("ipv6: use skb_expand_head in ip6_xmit") Signed-off-by: Eric Dumazet Cc: Vasily Averin Reviewed-by: David Ahern Link: https://patch.msgid.link/20240820160859.3786976-4-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

ipv6: fix possible UAF in ip6_finish_output2()

2025-01-09T12:24:59Z

[ Upstream commit e891b36de161fcd96f12ff83667473e5067b9037 ] If skb_expand_head() returns NULL, skb has been freed and associated dst/idev could also have been freed. We need to hold rcu_read_lock() to make sure the dst and associated idev are alive. Fixes: 5796015fa968 ("ipv6: allocate enough headroom in ip6_finish_output2()") Signed-off-by: Eric Dumazet Cc: Vasily Averin Reviewed-by: David Ahern Link: https://patch.msgid.link/20240820160859.3786976-3-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin (cherry picked from commit e891b36de161fcd96f12ff83667473e5067b9037) Signed-off-by: Harshvardhan Jha Signed-off-by: Sasha Levin

ipv6: use skb_expand_head in ip6_xmit

2025-01-09T12:24:59Z

[ Upstream commit 0c9f227bee11910a49e1d159abe102d06e3745d5 ] Unlike skb_realloc_headroom, new helper skb_expand_head does not allocate a new skb if possible. Additionally this patch replaces commonly used dereferencing with variables. Signed-off-by: Vasily Averin Signed-off-by: David S. Miller (cherry picked from commit 0c9f227bee11910a49e1d159abe102d06e3745d5) Signed-off-by: Harshvardhan Jha Signed-off-by: Sasha Levin

ipv6: use skb_expand_head in ip6_finish_output2

2025-01-09T12:24:59Z

[ Upstream commit e415ed3a4b8b246ee5e9d109ff5153efcf96b9f2 ] Unlike skb_realloc_headroom, new helper skb_expand_head does not allocate a new skb if possible. Additionally this patch replaces commonly used dereferencing with variables. Signed-off-by: Vasily Averin Signed-off-by: David S. Miller (cherry picked from commit e415ed3a4b8b246ee5e9d109ff5153efcf96b9f2) Signed-off-by: Harshvardhan Jha Signed-off-by: Sasha Levin

net: Add l3mdev index to flow struct and avoid oif reset for port devices

2024-10-17T13:08:35Z

[ Upstream commit 40867d74c374b235e14d839f3a77f26684feefe5 ] The fundamental premise of VRF and l3mdev core code is binding a socket to a device (l3mdev or netdev with an L3 domain) to indicate L3 scope. Legacy code resets flowi_oif to the l3mdev losing any original port device binding. Ben (among others) has demonstrated use cases where the original port device binding is important and needs to be retained. This patch handles that by adding a new entry to the common flow struct that can indicate the l3mdev index for later rule and table matching avoiding the need to reset flowi_oif. In addition to allowing more use cases that require port device binds, this patch brings a few datapath simplications: 1. l3mdev_fib_rule_match is only called when walking fib rules and always after l3mdev_update_flow. That allows an optimization to bail early for non-VRF type uses cases when flowi_l3mdev is not set. Also, only that index needs to be checked for the FIB table id. 2. l3mdev_update_flow can be called with flowi_oif set to a l3mdev (e.g., VRF) device. By resetting flowi_oif only for this case the FLOWI_FLAG_SKIP_NH_OIF flag is not longer needed and can be removed, removing several checks in the datapath. The flowi_iif path can be simplified to only be called if the it is not loopback (loopback can not be assigned to an L3 domain) and the l3mdev index is not already set. 3. Avoid another device lookup in the output path when the fib lookup returns a reject failure. Note: 2 functional tests for local traffic with reject fib rules are updated to reflect the new direct failure at FIB lookup time for ping rather than the failure on packet path. The current code fails like this: HINT: Fails since address on vrf device is out of device scope COMMAND: ip netns exec ns-A ping -c1 -w1 -I eth1 172.16.3.1 ping: Warning: source address might be selected on device other than: eth1 PING 172.16.3.1 (172.16.3.1) from 172.16.3.1 eth1: 56(84) bytes of data. --- 172.16.3.1 ping statistics --- 1 packets transmitted, 0 received, 100% packet loss, time 0ms where the test now directly fails: HINT: Fails since address on vrf device is out of device scope COMMAND: ip netns exec ns-A ping -c1 -w1 -I eth1 172.16.3.1 ping: connect: No route to host Signed-off-by: David Ahern Tested-by: Ben Greear Link: https://lore.kernel.org/r/20220314204551.16369-1-dsahern@kernel.org Signed-off-by: Jakub Kicinski Stable-dep-of: 05ef7055debc ("netfilter: fib: check correct rtable in vrf setups") Signed-off-by: Sasha Levin