Syzkaller managed to find a combination of actions that was generating
this warning:
WARNING: net/mptcp/pm_kernel.c:1074 at __mark_subflow_endp_available net/mptcp/pm_kernel.c:1074 [inline], CPU#1: syz.7.48/2535
WARNING: net/mptcp/pm_kernel.c:1074 at mptcp_pm_nl_fullmesh net/mptcp/pm_kernel.c:1446 [inline], CPU#1: syz.7.48/2535
WARNING: net/mptcp/pm_kernel.c:1074 at mptcp_pm_nl_set_flags_all net/mptcp/pm_kernel.c:1474 [inline], CPU#1: syz.7.48/2535
WARNING: net/mptcp/pm_kernel.c:1074 at mptcp_pm_nl_set_flags+0x5de/0x640 net/mptcp/pm_kernel.c:1538, CPU#1: syz.7.48/2535
Modules linked in:
CPU: 1 UID: 0 PID: 2535 Comm: syz.7.48 Not tainted 6.18.0-03987-gea5f5e676cf5 #17 PREEMPT(voluntary)
Hardware name: QEMU Ubuntu 25.10 PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014
RIP: 0010:__mark_subflow_endp_available net/mptcp/pm_kernel.c:1074 [inline]
RIP: 0010:mptcp_pm_nl_fullmesh net/mptcp/pm_kernel.c:1446 [inline]
RIP: 0010:mptcp_pm_nl_set_flags_all net/mptcp/pm_kernel.c:1474 [inline]
RIP: 0010:mptcp_pm_nl_set_flags+0x5de/0x640 net/mptcp/pm_kernel.c:1538
Code: 89 c7 e8 c5 8c 73 fe e9 f7 fd ff ff 49 83 ef 80 e8 b7 8c 73 fe 4c 89 ff be 03 00 00 00 e8 4a 29 e3 fe eb ac e8 a3 8c 73 fe 90 <0f> 0b 90 e9 3d ff ff ff e8 95 8c 73 fe b8 a1 ff ff ff eb 1a e8 89
RSP: 0018:ffffc9001535b820 EFLAGS: 00010287
netdevsim0: tun_chr_ioctl cmd 1074025677
RAX: ffffffff82da294d RBX: 0000000000000001 RCX: 0000000000080000
RDX: ffffc900096d0000 RSI: 00000000000006d6 RDI: 00000000000006d7
netdevsim0: linktype set to 823
RBP: ffff88802cdb2240 R08: 00000000000104ae R09: ffffffffffffffff
R10: ffffffff82da27d4 R11: 0000000000000000 R12: 0000000000000000
R13: ffff88801246d8c0 R14: ffffc9001535b8b8 R15: ffff88802cdb1800
FS: 00007fc6ac5a76c0(0000) GS:ffff8880f90c8000(0000) knlGS:0000000000000000
netlink: 'syz.3.50': attribute type 5 has an invalid length.
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
netlink: 1232 bytes leftover after parsing attributes in process `syz.3.50'.
CR2: 0000200000010000 CR3: 0000000025b1a000 CR4: 0000000000350ef0
Call Trace:
<TASK>
mptcp_pm_set_flags net/mptcp/pm_netlink.c:277 [inline]
mptcp_pm_nl_set_flags_doit+0x1d7/0x210 net/mptcp/pm_netlink.c:282
genl_family_rcv_msg_doit+0x117/0x180 net/netlink/genetlink.c:1115
genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
genl_rcv_msg+0x3a8/0x3f0 net/netlink/genetlink.c:1210
netlink_rcv_skb+0x16d/0x240 net/netlink/af_netlink.c:2550
genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
netlink_unicast+0x3e9/0x4c0 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x4ab/0x5b0 net/netlink/af_netlink.c:1894
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg+0xc9/0xf0 net/socket.c:733
____sys_sendmsg+0x272/0x3b0 net/socket.c:2608
___sys_sendmsg+0x2de/0x320 net/socket.c:2662
__sys_sendmsg net/socket.c:2694 [inline]
__do_sys_sendmsg net/socket.c:2699 [inline]
__se_sys_sendmsg net/socket.c:2697 [inline]
__x64_sys_sendmsg+0x110/0x1a0 net/socket.c:2697
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xed/0x360 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc6adb66f6d
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 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:00007fc6ac5a6ff8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fc6addf5fa0 RCX: 00007fc6adb66f6d
RDX: 0000000000048084 RSI: 00002000000002c0 RDI: 000000000000000e
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
netlink: 'syz.5.51': attribute type 2 has an invalid length.
R13: 00007fff25e91fe0 R14: 00007fc6ac5a7ce4 R15: 00007fff25e920d7
</TASK>
The actions that caused that seem to be:
- Create an MPTCP endpoint for address A without any flags
- Create a new MPTCP connection from address A
- Remove the MPTCP endpoint: the corresponding subflows will be removed
- Recreate the endpoint with the same ID, but with the subflow flag
- Change the same endpoint to add the fullmesh flag
In this case, msk->pm.local_addr_used has been decremented, but the
corresponding bit in msk->pm.id_avail_bitmap has not been reset.
When removing an endpoint, the corresponding endpoint ID was only marked
as available for announced addresses, not the other types. In these
cases, re-creating an endpoint with the same ID didn't signal/create
anything. Adding the fullmesh flag was creating the splat when calling
__mark_subflow_endp_available() from mptcp_pm_nl_fullmesh(), because
msk->pm.local_addr_used was set to 0 while the ID was marked as used.
Note: instead of adding a new spin_(un)lock_bh that would be taken in
all cases, do all the actions requiring the spin lock under the same
block.
This modification potentially fixes another issue reported by syzbot,
see [1]. But without a reproducer or more details about what exactly
happened before, it is hard to confirm.
Fixes: e255683c06df ("mptcp: pm: re-using ID of unused removed ADD_ADDR")
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/606
Reported-by: syzbot+f56f7d56e2c6e11a01b6@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/68fcfc4a.050a0220.346f24.02fb.GAE@google.com [1]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
net/mptcp/pm_kernel.c | 19 +++++++------------
1 file changed, 7 insertions(+), 12 deletions(-)
diff --git a/net/mptcp/pm_kernel.c b/net/mptcp/pm_kernel.c
index f59d21e7579c..51bcfcec882d 100644
--- a/net/mptcp/pm_kernel.c
+++ b/net/mptcp/pm_kernel.c
@@ -1057,10 +1057,8 @@ static bool mptcp_pm_remove_anno_addr(struct mptcp_sock *msk,
ret = mptcp_remove_anno_list_by_saddr(msk, addr);
if (ret || force) {
spin_lock_bh(&msk->pm.lock);
- if (ret) {
- __set_bit(addr->id, msk->pm.id_avail_bitmap);
+ if (ret)
msk->pm.add_addr_signaled--;
- }
mptcp_pm_remove_addr(msk, &list);
spin_unlock_bh(&msk->pm.lock);
}
@@ -1098,17 +1096,14 @@ static int mptcp_nl_remove_subflow_and_signal_addr(struct net *net,
!(entry->flags & MPTCP_PM_ADDR_FLAG_IMPLICIT));
list.ids[0] = mptcp_endp_get_local_id(msk, addr);
- if (remove_subflow) {
- spin_lock_bh(&msk->pm.lock);
- mptcp_pm_rm_subflow(msk, &list);
- spin_unlock_bh(&msk->pm.lock);
- }
- if (entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW) {
- spin_lock_bh(&msk->pm.lock);
+ spin_lock_bh(&msk->pm.lock);
+ if (remove_subflow)
+ mptcp_pm_rm_subflow(msk, &list);
+ if (entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW)
__mark_subflow_endp_available(msk, list.ids[0]);
- spin_unlock_bh(&msk->pm.lock);
- }
+ __set_bit(addr->id, msk->pm.id_avail_bitmap);
+ spin_unlock_bh(&msk->pm.lock);
if (msk->mpc_endpoint_id == entry->addr.id)
msk->mpc_endpoint_id = 0;
--
2.51.0On Mon, 15 Dec 2025, Matthieu Baerts (NGI0) wrote:
> Syzkaller managed to find a combination of actions that was generating
> this warning:
>
> WARNING: net/mptcp/pm_kernel.c:1074 at __mark_subflow_endp_available net/mptcp/pm_kernel.c:1074 [inline], CPU#1: syz.7.48/2535
> WARNING: net/mptcp/pm_kernel.c:1074 at mptcp_pm_nl_fullmesh net/mptcp/pm_kernel.c:1446 [inline], CPU#1: syz.7.48/2535
> WARNING: net/mptcp/pm_kernel.c:1074 at mptcp_pm_nl_set_flags_all net/mptcp/pm_kernel.c:1474 [inline], CPU#1: syz.7.48/2535
> WARNING: net/mptcp/pm_kernel.c:1074 at mptcp_pm_nl_set_flags+0x5de/0x640 net/mptcp/pm_kernel.c:1538, CPU#1: syz.7.48/2535
> Modules linked in:
> CPU: 1 UID: 0 PID: 2535 Comm: syz.7.48 Not tainted 6.18.0-03987-gea5f5e676cf5 #17 PREEMPT(voluntary)
> Hardware name: QEMU Ubuntu 25.10 PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014
> RIP: 0010:__mark_subflow_endp_available net/mptcp/pm_kernel.c:1074 [inline]
> RIP: 0010:mptcp_pm_nl_fullmesh net/mptcp/pm_kernel.c:1446 [inline]
> RIP: 0010:mptcp_pm_nl_set_flags_all net/mptcp/pm_kernel.c:1474 [inline]
> RIP: 0010:mptcp_pm_nl_set_flags+0x5de/0x640 net/mptcp/pm_kernel.c:1538
> Code: 89 c7 e8 c5 8c 73 fe e9 f7 fd ff ff 49 83 ef 80 e8 b7 8c 73 fe 4c 89 ff be 03 00 00 00 e8 4a 29 e3 fe eb ac e8 a3 8c 73 fe 90 <0f> 0b 90 e9 3d ff ff ff e8 95 8c 73 fe b8 a1 ff ff ff eb 1a e8 89
> RSP: 0018:ffffc9001535b820 EFLAGS: 00010287
> netdevsim0: tun_chr_ioctl cmd 1074025677
> RAX: ffffffff82da294d RBX: 0000000000000001 RCX: 0000000000080000
> RDX: ffffc900096d0000 RSI: 00000000000006d6 RDI: 00000000000006d7
> netdevsim0: linktype set to 823
> RBP: ffff88802cdb2240 R08: 00000000000104ae R09: ffffffffffffffff
> R10: ffffffff82da27d4 R11: 0000000000000000 R12: 0000000000000000
> R13: ffff88801246d8c0 R14: ffffc9001535b8b8 R15: ffff88802cdb1800
> FS: 00007fc6ac5a76c0(0000) GS:ffff8880f90c8000(0000) knlGS:0000000000000000
> netlink: 'syz.3.50': attribute type 5 has an invalid length.
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> netlink: 1232 bytes leftover after parsing attributes in process `syz.3.50'.
> CR2: 0000200000010000 CR3: 0000000025b1a000 CR4: 0000000000350ef0
> Call Trace:
> <TASK>
> mptcp_pm_set_flags net/mptcp/pm_netlink.c:277 [inline]
> mptcp_pm_nl_set_flags_doit+0x1d7/0x210 net/mptcp/pm_netlink.c:282
> genl_family_rcv_msg_doit+0x117/0x180 net/netlink/genetlink.c:1115
> genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
> genl_rcv_msg+0x3a8/0x3f0 net/netlink/genetlink.c:1210
> netlink_rcv_skb+0x16d/0x240 net/netlink/af_netlink.c:2550
> genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
> netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
> netlink_unicast+0x3e9/0x4c0 net/netlink/af_netlink.c:1344
> netlink_sendmsg+0x4ab/0x5b0 net/netlink/af_netlink.c:1894
> sock_sendmsg_nosec net/socket.c:718 [inline]
> __sock_sendmsg+0xc9/0xf0 net/socket.c:733
> ____sys_sendmsg+0x272/0x3b0 net/socket.c:2608
> ___sys_sendmsg+0x2de/0x320 net/socket.c:2662
> __sys_sendmsg net/socket.c:2694 [inline]
> __do_sys_sendmsg net/socket.c:2699 [inline]
> __se_sys_sendmsg net/socket.c:2697 [inline]
> __x64_sys_sendmsg+0x110/0x1a0 net/socket.c:2697
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xed/0x360 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fc6adb66f6d
> Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 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:00007fc6ac5a6ff8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> RAX: ffffffffffffffda RBX: 00007fc6addf5fa0 RCX: 00007fc6adb66f6d
> RDX: 0000000000048084 RSI: 00002000000002c0 RDI: 000000000000000e
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> netlink: 'syz.5.51': attribute type 2 has an invalid length.
> R13: 00007fff25e91fe0 R14: 00007fc6ac5a7ce4 R15: 00007fff25e920d7
> </TASK>
>
> The actions that caused that seem to be:
>
> - Create an MPTCP endpoint for address A without any flags
> - Create a new MPTCP connection from address A
> - Remove the MPTCP endpoint: the corresponding subflows will be removed
> - Recreate the endpoint with the same ID, but with the subflow flag
> - Change the same endpoint to add the fullmesh flag
>
> In this case, msk->pm.local_addr_used has been decremented, but the
> corresponding bit in msk->pm.id_avail_bitmap has not been reset.
>
> When removing an endpoint, the corresponding endpoint ID was only marked
> as available for announced addresses, not the other types. In these
> cases, re-creating an endpoint with the same ID didn't signal/create
> anything. Adding the fullmesh flag was creating the splat when calling
> __mark_subflow_endp_available() from mptcp_pm_nl_fullmesh(), because
> msk->pm.local_addr_used was set to 0 while the ID was marked as used.
>
> Note: instead of adding a new spin_(un)lock_bh that would be taken in
> all cases, do all the actions requiring the spin lock under the same
> block.
>
> This modification potentially fixes another issue reported by syzbot,
> see [1]. But without a reproducer or more details about what exactly
> happened before, it is hard to confirm.
>
> Fixes: e255683c06df ("mptcp: pm: re-using ID of unused removed ADD_ADDR")
> Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/606
> Reported-by: syzbot+f56f7d56e2c6e11a01b6@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/68fcfc4a.050a0220.346f24.02fb.GAE@google.com [1]
> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
> ---
> net/mptcp/pm_kernel.c | 19 +++++++------------
> 1 file changed, 7 insertions(+), 12 deletions(-)
>
> diff --git a/net/mptcp/pm_kernel.c b/net/mptcp/pm_kernel.c
> index f59d21e7579c..51bcfcec882d 100644
> --- a/net/mptcp/pm_kernel.c
> +++ b/net/mptcp/pm_kernel.c
> @@ -1057,10 +1057,8 @@ static bool mptcp_pm_remove_anno_addr(struct mptcp_sock *msk,
> ret = mptcp_remove_anno_list_by_saddr(msk, addr);
> if (ret || force) {
> spin_lock_bh(&msk->pm.lock);
> - if (ret) {
> - __set_bit(addr->id, msk->pm.id_avail_bitmap);
> + if (ret)
> msk->pm.add_addr_signaled--;
> - }
> mptcp_pm_remove_addr(msk, &list);
> spin_unlock_bh(&msk->pm.lock);
> }
> @@ -1098,17 +1096,14 @@ static int mptcp_nl_remove_subflow_and_signal_addr(struct net *net,
> !(entry->flags & MPTCP_PM_ADDR_FLAG_IMPLICIT));
>
> list.ids[0] = mptcp_endp_get_local_id(msk, addr);
> - if (remove_subflow) {
> - spin_lock_bh(&msk->pm.lock);
> - mptcp_pm_rm_subflow(msk, &list);
> - spin_unlock_bh(&msk->pm.lock);
> - }
>
> - if (entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW) {
> - spin_lock_bh(&msk->pm.lock);
> + spin_lock_bh(&msk->pm.lock);
> + if (remove_subflow)
> + mptcp_pm_rm_subflow(msk, &list);
> + if (entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW)
> __mark_subflow_endp_available(msk, list.ids[0]);
> - spin_unlock_bh(&msk->pm.lock);
> - }
> + __set_bit(addr->id, msk->pm.id_avail_bitmap);
There's not any harm in setting this bit a second time if it was also set
in __mark_subflow_endp_available().
However, __mark_subflow_endp_available() has some logic around ID 0 and
mpc_endpoint_id. Is that relevant in this code path or is the new
__set_bit() doing the correct thing by always clearing based on addr->id?
- Mat
> + spin_unlock_bh(&msk->pm.lock);
>
> if (msk->mpc_endpoint_id == entry->addr.id)
> msk->mpc_endpoint_id = 0;
>
> --
> 2.51.0
>
>
>
Hi Mat,
Thank you for the review!
On 15/01/2026 05:56, Mat Martineau wrote:
> On Mon, 15 Dec 2025, Matthieu Baerts (NGI0) wrote:
>
>> Syzkaller managed to find a combination of actions that was generating
>> this warning:
(...)
>> diff --git a/net/mptcp/pm_kernel.c b/net/mptcp/pm_kernel.c
>> index f59d21e7579c..51bcfcec882d 100644
>> --- a/net/mptcp/pm_kernel.c
>> +++ b/net/mptcp/pm_kernel.c
>> @@ -1057,10 +1057,8 @@ static bool mptcp_pm_remove_anno_addr(struct
>> mptcp_sock *msk,
>> ret = mptcp_remove_anno_list_by_saddr(msk, addr);
>> if (ret || force) {
>> spin_lock_bh(&msk->pm.lock);
>> - if (ret) {
>> - __set_bit(addr->id, msk->pm.id_avail_bitmap);
>> + if (ret)
>> msk->pm.add_addr_signaled--;
>> - }
>> mptcp_pm_remove_addr(msk, &list);
>> spin_unlock_bh(&msk->pm.lock);
>> }
>> @@ -1098,17 +1096,14 @@ static int
>> mptcp_nl_remove_subflow_and_signal_addr(struct net *net,
>> !(entry->flags & MPTCP_PM_ADDR_FLAG_IMPLICIT));
>>
>> list.ids[0] = mptcp_endp_get_local_id(msk, addr);
>> - if (remove_subflow) {
>> - spin_lock_bh(&msk->pm.lock);
>> - mptcp_pm_rm_subflow(msk, &list);
>> - spin_unlock_bh(&msk->pm.lock);
>> - }
>>
>> - if (entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW) {
>> - spin_lock_bh(&msk->pm.lock);
>> + spin_lock_bh(&msk->pm.lock);
>> + if (remove_subflow)
>> + mptcp_pm_rm_subflow(msk, &list);
>> + if (entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW)
>> __mark_subflow_endp_available(msk, list.ids[0]);
>> - spin_unlock_bh(&msk->pm.lock);
>> - }
>> + __set_bit(addr->id, msk->pm.id_avail_bitmap);
>
> There's not any harm in setting this bit a second time if it was also
> set in __mark_subflow_endp_available().
>
> However, __mark_subflow_endp_available() has some logic around ID 0 and
> mpc_endpoint_id. Is that relevant in this code path or is the new
> __set_bit() doing the correct thing by always clearing based on addr->id?
Good point. Even if there is no harm, no need to set the bit for ID 0. I
will look at that!
Cheers,
Matt
--
Sponsored by the NGI0 Core fund.
Hi Mat,
On 26/01/2026 19:34, Matthieu Baerts wrote:
> Hi Mat,
>
> Thank you for the review!
>
> On 15/01/2026 05:56, Mat Martineau wrote:
>> On Mon, 15 Dec 2025, Matthieu Baerts (NGI0) wrote:
>>
>>> Syzkaller managed to find a combination of actions that was generating
>>> this warning:
>
> (...)
>
>>> diff --git a/net/mptcp/pm_kernel.c b/net/mptcp/pm_kernel.c
>>> index f59d21e7579c..51bcfcec882d 100644
>>> --- a/net/mptcp/pm_kernel.c
>>> +++ b/net/mptcp/pm_kernel.c
>>> @@ -1057,10 +1057,8 @@ static bool mptcp_pm_remove_anno_addr(struct
>>> mptcp_sock *msk,
>>> ret = mptcp_remove_anno_list_by_saddr(msk, addr);
>>> if (ret || force) {
>>> spin_lock_bh(&msk->pm.lock);
>>> - if (ret) {
>>> - __set_bit(addr->id, msk->pm.id_avail_bitmap);
>>> + if (ret)
>>> msk->pm.add_addr_signaled--;
>>> - }
>>> mptcp_pm_remove_addr(msk, &list);
>>> spin_unlock_bh(&msk->pm.lock);
>>> }
>>> @@ -1098,17 +1096,14 @@ static int
>>> mptcp_nl_remove_subflow_and_signal_addr(struct net *net,
>>> !(entry->flags & MPTCP_PM_ADDR_FLAG_IMPLICIT));
>>>
>>> list.ids[0] = mptcp_endp_get_local_id(msk, addr);
>>> - if (remove_subflow) {
>>> - spin_lock_bh(&msk->pm.lock);
>>> - mptcp_pm_rm_subflow(msk, &list);
>>> - spin_unlock_bh(&msk->pm.lock);
>>> - }
>>>
>>> - if (entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW) {
>>> - spin_lock_bh(&msk->pm.lock);
>>> + spin_lock_bh(&msk->pm.lock);
>>> + if (remove_subflow)
>>> + mptcp_pm_rm_subflow(msk, &list);
>>> + if (entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW)
>>> __mark_subflow_endp_available(msk, list.ids[0]);
>>> - spin_unlock_bh(&msk->pm.lock);
>>> - }
>>> + __set_bit(addr->id, msk->pm.id_avail_bitmap);
>>
>> There's not any harm in setting this bit a second time if it was also
>> set in __mark_subflow_endp_available().
>>
>> However, __mark_subflow_endp_available() has some logic around ID 0 and
>> mpc_endpoint_id. Is that relevant in this code path or is the new
>> __set_bit() doing the correct thing by always clearing based on addr->id?
>
> Good point. Even if there is no harm, no need to set the bit for ID 0. I
> will look at that!
I just re-checked this: addr->id here is always positive because that's
the endpoint ID, not the ID used on the wire (list.ids[0]) which can be
0 if this endpoint is linked to the initial subflow. So we don't need
the same logic around ID 0 and mpc_endpoint_id.
Still, I can add this before calling __set_bit() not to clear the bit a
second time:
else /* mark endp ID as available, e.g. Signal or MPC endp */
Cheers,
Matt
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