| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2025-21771: sched_ext: Fix incorrect autogroup migration detection |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| sched_ext: Fix incorrect autogroup migration detection |
| |
| scx_move_task() is called from sched_move_task() and tells the BPF scheduler |
| that cgroup migration is being committed. sched_move_task() is used by both |
| cgroup and autogroup migrations and scx_move_task() tried to filter out |
| autogroup migrations by testing the destination cgroup and PF_EXITING but |
| this is not enough. In fact, without explicitly tagging the thread which is |
| doing the cgroup migration, there is no good way to tell apart |
| scx_move_task() invocations for racing migration to the root cgroup and an |
| autogroup migration. |
| |
| This led to scx_move_task() incorrectly ignoring a migration from non-root |
| cgroup to an autogroup of the root cgroup triggering the following warning: |
| |
| WARNING: CPU: 7 PID: 1 at kernel/sched/ext.c:3725 scx_cgroup_can_attach+0x196/0x340 |
| ... |
| Call Trace: |
| <TASK> |
| cgroup_migrate_execute+0x5b1/0x700 |
| cgroup_attach_task+0x296/0x400 |
| __cgroup_procs_write+0x128/0x140 |
| cgroup_procs_write+0x17/0x30 |
| kernfs_fop_write_iter+0x141/0x1f0 |
| vfs_write+0x31d/0x4a0 |
| __x64_sys_write+0x72/0xf0 |
| do_syscall_64+0x82/0x160 |
| entry_SYSCALL_64_after_hwframe+0x76/0x7e |
| |
| Fix it by adding an argument to sched_move_task() that indicates whether the |
| moving is for a cgroup or autogroup migration. After the change, |
| scx_move_task() is called only for cgroup migrations and renamed to |
| scx_cgroup_move_task(). |
| |
| The Linux kernel CVE team has assigned CVE-2025-21771 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.12 with commit 8195136669661fdfe54e9a8923c33b31c92fc1da and fixed in 6.12.16 with commit 75bf2f80c046d2ec5a07455891ea0a9fb6d8b5f6 |
| Issue introduced in 6.12 with commit 8195136669661fdfe54e9a8923c33b31c92fc1da and fixed in 6.13.4 with commit d8b510d0ddc65d8a71e0f9a3acc9ed5f010fc514 |
| Issue introduced in 6.12 with commit 8195136669661fdfe54e9a8923c33b31c92fc1da and fixed in 6.14 with commit d6f3e7d564b2309e1f17e709a70eca78d7ca2bb8 |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2025-21771 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| kernel/sched/autogroup.c |
| kernel/sched/core.c |
| kernel/sched/ext.c |
| kernel/sched/ext.h |
| kernel/sched/sched.h |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/75bf2f80c046d2ec5a07455891ea0a9fb6d8b5f6 |
| https://git.kernel.org/stable/c/d8b510d0ddc65d8a71e0f9a3acc9ed5f010fc514 |
| https://git.kernel.org/stable/c/d6f3e7d564b2309e1f17e709a70eca78d7ca2bb8 |
