CVE-2025-71142

In the Linux kernel, the following vulnerability has been resolved:

cpuset: fix warning when disabling remote partition

A warning was triggered as follows:

WARNING: kernel/cgroup/cpuset.c:1651 at remotepartitiondisable+0xf7/0x110 RIP: 0010:remotepartitiondisable+0xf7/0x110 RSP: 0018:ffffc90001947d88 EFLAGS: 00000206 RAX: 0000000000007fff RBX: ffff888103b6e000 RCX: 0000000000006f40 RDX: 0000000000006f00 RSI: ffffc90001947da8 RDI: ffff888103b6e000 RBP: ffff888103b6e000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000001 R11: ffff88810b2e2728 R12: ffffc90001947da8 R13: 0000000000000000 R14: ffffc90001947da8 R15: ffff8881081f1c00 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f55c8bbe0b2 CR3: 000000010b14c000 CR4: 00000000000006f0 Call Trace: <TASK> updateprstate+0x2d3/0x580 cpusetpartitionwrite+0x94/0xf0 kernfsfopwriteiter+0x147/0x200 vfswrite+0x35d/0x500 ksyswrite+0x66/0xe0 dosyscall64+0x6b/0x390 entrySYSCALL64afterhwframe+0x4b/0x53 RIP: 0033:0x7f55c8cd4887

Reproduction steps (on a 16-CPU machine):

    # cd /sys/fs/cgroup/
    # mkdir A1
    # echo +cpuset > A1/cgroup.subtree_control
    # echo "0-14" > A1/cpuset.cpus.exclusive
    # mkdir A1/A2
    # echo "0-14" > A1/A2/cpuset.cpus.exclusive
    # echo "root" > A1/A2/cpuset.cpus.partition
    # echo 0 > /sys/devices/system/cpu/cpu15/online
    # echo member > A1/A2/cpuset.cpus.partition

When CPU 15 is offlined, subpartitionscpus gets cleared because no CPUs remain available for the topcpuset, forcing partitions to share CPUs with the topcpuset. In this scenario, disabling the remote partition triggers a warning stating that effectivexcpus is not a subset of subpartitionscpus. Partitions should be invalidated in this case to inform users that the partition is now invalid(cpus are shared with topcpuset).

To fix this issue: 1. Only emit the warning only if subpartitionscpus is not empty and the effectivexcpus is not a subset of subpartitionscpus. 2. During the CPU hotplug process, invalidate partitions if subpartitionscpus is empty.