Here are two unrelated fixes, plus an extra patch:
- Patch 1: prevent a warning by removing an unneeded and incorrect small optimisation in the path-manager. A fix for v5.10.
- Patch 2: reset a subflow when MPTCP opts have been dropped after having correctly added a new path. A fix for v5.19.
- Patch 3: add a safety check to prevent issues like the one fixed by the second patch.
Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org --- Matthieu Baerts (NGI0) (2): mptcp: reset when MPTCP opts are dropped after join mptcp: safety check before fallback
Paolo Abeni (1): mptcp: always handle address removal under msk socket lock
net/mptcp/pm_netlink.c | 5 ----- net/mptcp/protocol.h | 2 ++ net/mptcp/subflow.c | 15 +-------------- 3 files changed, 3 insertions(+), 19 deletions(-) --- base-commit: f15176b8b6e72ac30e14fd273282d2b72562d26b change-id: 20250224-net-mptcp-misc-fixes-8af87640dfef
Best regards,
From: Paolo Abeni pabeni@redhat.com
Syzkaller reported a lockdep splat in the PM control path:
WARNING: CPU: 0 PID: 6693 at ./include/net/sock.h:1711 sock_owned_by_me include/net/sock.h:1711 [inline] WARNING: CPU: 0 PID: 6693 at ./include/net/sock.h:1711 msk_owned_by_me net/mptcp/protocol.h:363 [inline] WARNING: CPU: 0 PID: 6693 at ./include/net/sock.h:1711 mptcp_pm_nl_addr_send_ack+0x57c/0x610 net/mptcp/pm_netlink.c:788 Modules linked in: CPU: 0 UID: 0 PID: 6693 Comm: syz.0.205 Not tainted 6.14.0-rc2-syzkaller-00303-gad1b832bf1cf #0 Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024 RIP: 0010:sock_owned_by_me include/net/sock.h:1711 [inline] RIP: 0010:msk_owned_by_me net/mptcp/protocol.h:363 [inline] RIP: 0010:mptcp_pm_nl_addr_send_ack+0x57c/0x610 net/mptcp/pm_netlink.c:788 Code: 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc e8 ca 7b d3 f5 eb b9 e8 c3 7b d3 f5 90 0f 0b 90 e9 dd fb ff ff e8 b5 7b d3 f5 90 <0f> 0b 90 e9 3e fb ff ff 44 89 f1 80 e1 07 38 c1 0f 8c eb fb ff ff RSP: 0000:ffffc900034f6f60 EFLAGS: 00010283 RAX: ffffffff8bee3c2b RBX: 0000000000000001 RCX: 0000000000080000 RDX: ffffc90004d42000 RSI: 000000000000a407 RDI: 000000000000a408 RBP: ffffc900034f7030 R08: ffffffff8bee37f6 R09: 0100000000000000 R10: dffffc0000000000 R11: ffffed100bcc62e4 R12: ffff88805e6316e0 R13: ffff88805e630c00 R14: dffffc0000000000 R15: ffff88805e630c00 FS: 00007f7e9a7e96c0(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b2fd18ff8 CR3: 0000000032c24000 CR4: 00000000003526f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> mptcp_pm_remove_addr+0x103/0x1d0 net/mptcp/pm.c:59 mptcp_pm_remove_anno_addr+0x1f4/0x2f0 net/mptcp/pm_netlink.c:1486 mptcp_nl_remove_subflow_and_signal_addr net/mptcp/pm_netlink.c:1518 [inline] mptcp_pm_nl_del_addr_doit+0x118d/0x1af0 net/mptcp/pm_netlink.c:1629 genl_family_rcv_msg_doit net/netlink/genetlink.c:1115 [inline] genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline] genl_rcv_msg+0xb1f/0xec0 net/netlink/genetlink.c:1210 netlink_rcv_skb+0x206/0x480 net/netlink/af_netlink.c:2543 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219 netlink_unicast_kernel net/netlink/af_netlink.c:1322 [inline] netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1348 netlink_sendmsg+0x8de/0xcb0 net/netlink/af_netlink.c:1892 sock_sendmsg_nosec net/socket.c:718 [inline] __sock_sendmsg+0x221/0x270 net/socket.c:733 ____sys_sendmsg+0x53a/0x860 net/socket.c:2573 ___sys_sendmsg net/socket.c:2627 [inline] __sys_sendmsg+0x269/0x350 net/socket.c:2659 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f7e9998cde9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f7e9a7e9038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f7e99ba5fa0 RCX: 00007f7e9998cde9 RDX: 000000002000c094 RSI: 0000400000000000 RDI: 0000000000000007 RBP: 00007f7e99a0e2a0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f7e99ba5fa0 R15: 00007fff49231088
Indeed the PM can try to send a RM_ADDR over a msk without acquiring first the msk socket lock.
The bugged code-path comes from an early optimization: when there are no subflows, the PM should (usually) not send RM_ADDR notifications.
The above statement is incorrect, as without locks another process could concurrent create a new subflow and cause the RM_ADDR generation.
Additionally the supposed optimization is not very effective even performance-wise, as most mptcp sockets should have at least one subflow: the MPC one.
Address the issue removing the buggy code path, the existing "slow-path" will handle correctly even the edge case.
Fixes: b6c08380860b ("mptcp: remove addr and subflow in PM netlink") Cc: stable@vger.kernel.org Reported-by: syzbot+cd3ce3d03a3393ae9700@syzkaller.appspotmail.com Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/546 Signed-off-by: Paolo Abeni pabeni@redhat.com Reviewed-by: Matthieu Baerts (NGI0) matttbe@kernel.org Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org --- net/mptcp/pm_netlink.c | 5 ----- 1 file changed, 5 deletions(-)
diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c index 572d160edca33c0a941203d8ae0b0bde0f2ef3e2..c0e47f4f7b1aa2fedf615c44ea595c1f9d2528f9 100644 --- a/net/mptcp/pm_netlink.c +++ b/net/mptcp/pm_netlink.c @@ -1514,11 +1514,6 @@ static int mptcp_nl_remove_subflow_and_signal_addr(struct net *net, if (mptcp_pm_is_userspace(msk)) goto next;
- if (list_empty(&msk->conn_list)) { - mptcp_pm_remove_anno_addr(msk, addr, false); - goto next; - } - lock_sock(sk); remove_subflow = mptcp_lookup_subflow_by_saddr(&msk->conn_list, addr); mptcp_pm_remove_anno_addr(msk, addr, remove_subflow &&
Before this patch, if the checksum was not used, the subflow was only reset if map_data_len was != 0. If there were no MPTCP options or an invalid mapping, map_data_len was not set to the data len, and then the subflow was not reset as it should have been, leaving the MPTCP connection in a wrong fallback mode.
This map_data_len condition has been introduced to handle the reception of the infinite mapping. Instead, a new dedicated mapping error could have been returned and treated as a special case. However, the commit 31bf11de146c ("mptcp: introduce MAPPING_BAD_CSUM") has been introduced by Paolo Abeni soon after, and backported later on to stable. It better handle the csum case, and it means the exception for valid_csum_seen in subflow_can_fallback(), plus this one for the infinite mapping in subflow_check_data_avail(), are no longer needed.
In other words, the code can be simplified there: a fallback should only be done if msk->allow_infinite_fallback is set. This boolean is set to false once MPTCP-specific operations acting on the whole MPTCP connection vs the initial path have been done, e.g. a second path has been created, or an MPTCP re-injection -- yes, possible even with a single subflow. The subflow_can_fallback() helper can then be dropped, and replaced by this single condition.
This also makes the code clearer: a fallback should only be done if it is possible to do so.
While at it, no need to set map_data_len to 0 in get_mapping_status() for the infinite mapping case: it will be set to skb->len just after, at the end of subflow_check_data_avail(), and not read in between.
Fixes: f8d4bcacff3b ("mptcp: infinite mapping receiving") Cc: stable@vger.kernel.org Reported-by: Chester A. Unal chester.a.unal@xpedite-tech.com Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/544 Acked-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org --- net/mptcp/subflow.c | 15 +-------------- 1 file changed, 1 insertion(+), 14 deletions(-)
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index dfcbef9c46246983d21c827d9551d4eb2c95430e..9f18217dddc865bc467a2c5c34aa4bf23bf3ac75 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -1142,7 +1142,6 @@ static enum mapping_status get_mapping_status(struct sock *ssk, if (data_len == 0) { pr_debug("infinite mapping received\n"); MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_INFINITEMAPRX); - subflow->map_data_len = 0; return MAPPING_INVALID; }
@@ -1286,18 +1285,6 @@ static void subflow_sched_work_if_closed(struct mptcp_sock *msk, struct sock *ss mptcp_schedule_work(sk); }
-static bool subflow_can_fallback(struct mptcp_subflow_context *subflow) -{ - struct mptcp_sock *msk = mptcp_sk(subflow->conn); - - if (subflow->mp_join) - return false; - else if (READ_ONCE(msk->csum_enabled)) - return !subflow->valid_csum_seen; - else - return READ_ONCE(msk->allow_infinite_fallback); -} - static void mptcp_subflow_fail(struct mptcp_sock *msk, struct sock *ssk) { struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk); @@ -1393,7 +1380,7 @@ static bool subflow_check_data_avail(struct sock *ssk) return true; }
- if (!subflow_can_fallback(subflow) && subflow->map_data_len) { + if (!READ_ONCE(msk->allow_infinite_fallback)) { /* fatal protocol error, close the socket. * subflow_error_report() will introduce the appropriate barriers */
Tested-by: Chester A. Unal chester.a.unal@xpedite-tech.com
Thanks a ton! Chester A.
On Mon, Feb 24, 2025 at 6:19 PM Matthieu Baerts (NGI0) matttbe@kernel.org wrote:
Before this patch, if the checksum was not used, the subflow was only reset if map_data_len was != 0. If there were no MPTCP options or an invalid mapping, map_data_len was not set to the data len, and then the subflow was not reset as it should have been, leaving the MPTCP connection in a wrong fallback mode.
This map_data_len condition has been introduced to handle the reception of the infinite mapping. Instead, a new dedicated mapping error could have been returned and treated as a special case. However, the commit 31bf11de146c ("mptcp: introduce MAPPING_BAD_CSUM") has been introduced by Paolo Abeni soon after, and backported later on to stable. It better handle the csum case, and it means the exception for valid_csum_seen in subflow_can_fallback(), plus this one for the infinite mapping in subflow_check_data_avail(), are no longer needed.
In other words, the code can be simplified there: a fallback should only be done if msk->allow_infinite_fallback is set. This boolean is set to false once MPTCP-specific operations acting on the whole MPTCP connection vs the initial path have been done, e.g. a second path has been created, or an MPTCP re-injection -- yes, possible even with a single subflow. The subflow_can_fallback() helper can then be dropped, and replaced by this single condition.
This also makes the code clearer: a fallback should only be done if it is possible to do so.
While at it, no need to set map_data_len to 0 in get_mapping_status() for the infinite mapping case: it will be set to skb->len just after, at the end of subflow_check_data_avail(), and not read in between.
Fixes: f8d4bcacff3b ("mptcp: infinite mapping receiving") Cc: stable@vger.kernel.org Reported-by: Chester A. Unal chester.a.unal@xpedite-tech.com Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/544 Acked-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org
net/mptcp/subflow.c | 15 +-------------- 1 file changed, 1 insertion(+), 14 deletions(-)
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index dfcbef9c46246983d21c827d9551d4eb2c95430e..9f18217dddc865bc467a2c5c34aa4bf23bf3ac75 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -1142,7 +1142,6 @@ static enum mapping_status get_mapping_status(struct sock *ssk, if (data_len == 0) { pr_debug("infinite mapping received\n"); MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_INFINITEMAPRX);
subflow->map_data_len = 0; return MAPPING_INVALID; }@@ -1286,18 +1285,6 @@ static void subflow_sched_work_if_closed(struct mptcp_sock *msk, struct sock *ss mptcp_schedule_work(sk); }
-static bool subflow_can_fallback(struct mptcp_subflow_context *subflow) -{
struct mptcp_sock *msk = mptcp_sk(subflow->conn);if (subflow->mp_join)return false;else if (READ_ONCE(msk->csum_enabled))return !subflow->valid_csum_seen;elsereturn READ_ONCE(msk->allow_infinite_fallback);-}
static void mptcp_subflow_fail(struct mptcp_sock *msk, struct sock *ssk) { struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk); @@ -1393,7 +1380,7 @@ static bool subflow_check_data_avail(struct sock *ssk) return true; }
if (!subflow_can_fallback(subflow) && subflow->map_data_len) {
if (!READ_ONCE(msk->allow_infinite_fallback)) { /* fatal protocol error, close the socket. * subflow_error_report() will introduce the appropriate barriers */-- 2.47.1
Hello:
This series was applied to netdev/net.git (main) by Jakub Kicinski kuba@kernel.org:
On Mon, 24 Feb 2025 19:11:49 +0100 you wrote:
Here are two unrelated fixes, plus an extra patch:
Patch 1: prevent a warning by removing an unneeded and incorrect small optimisation in the path-manager. A fix for v5.10.
Patch 2: reset a subflow when MPTCP opts have been dropped after having correctly added a new path. A fix for v5.19.
[...]
Here is the summary with links: - [net,1/3] mptcp: always handle address removal under msk socket lock https://git.kernel.org/netdev/net/c/f865c24bc551 - [net,2/3] mptcp: reset when MPTCP opts are dropped after join https://git.kernel.org/netdev/net/c/8668860b0ad3 - [net,3/3] mptcp: safety check before fallback https://git.kernel.org/netdev/net/c/db75a16813aa
You are awesome, thank you!
linux-stable-mirror@lists.linaro.org
-
Chester A. Unal -
Matthieu Baerts (NGI0) -
patchwork-bot+netdevbpf＠kernel.org