| 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-2022-48892: sched/core: Fix use-after-free bug in dup_user_cpus_ptr() |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| sched/core: Fix use-after-free bug in dup_user_cpus_ptr() |
| |
| Since commit 07ec77a1d4e8 ("sched: Allow task CPU affinity to be |
| restricted on asymmetric systems"), the setting and clearing of |
| user_cpus_ptr are done under pi_lock for arm64 architecture. However, |
| dup_user_cpus_ptr() accesses user_cpus_ptr without any lock |
| protection. Since sched_setaffinity() can be invoked from another |
| process, the process being modified may be undergoing fork() at |
| the same time. When racing with the clearing of user_cpus_ptr in |
| __set_cpus_allowed_ptr_locked(), it can lead to user-after-free and |
| possibly double-free in arm64 kernel. |
| |
| Commit 8f9ea86fdf99 ("sched: Always preserve the user requested |
| cpumask") fixes this problem as user_cpus_ptr, once set, will never |
| be cleared in a task's lifetime. However, this bug was re-introduced |
| in commit 851a723e45d1 ("sched: Always clear user_cpus_ptr in |
| do_set_cpus_allowed()") which allows the clearing of user_cpus_ptr in |
| do_set_cpus_allowed(). This time, it will affect all arches. |
| |
| Fix this bug by always clearing the user_cpus_ptr of the newly |
| cloned/forked task before the copying process starts and check the |
| user_cpus_ptr state of the source task under pi_lock. |
| |
| Note to stable, this patch won't be applicable to stable releases. |
| Just copy the new dup_user_cpus_ptr() function over. |
| |
| The Linux kernel CVE team has assigned CVE-2022-48892 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.15 with commit 07ec77a1d4e82526e1588979fff2f024f8e96df2 and fixed in 5.15.89 with commit b22faa21b6230d5eccd233e1b7e0026a5002b287 |
| Issue introduced in 5.15 with commit 07ec77a1d4e82526e1588979fff2f024f8e96df2 and fixed in 6.1.7 with commit 7b5cc7fd1789ea5dbb942c9f8207b076d365badc |
| Issue introduced in 5.15 with commit 07ec77a1d4e82526e1588979fff2f024f8e96df2 and fixed in 6.2 with commit 87ca4f9efbd7cc649ff43b87970888f2812945b8 |
| |
| 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-2022-48892 |
| 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/core.c |
| |
| |
| 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/b22faa21b6230d5eccd233e1b7e0026a5002b287 |
| https://git.kernel.org/stable/c/7b5cc7fd1789ea5dbb942c9f8207b076d365badc |
| https://git.kernel.org/stable/c/87ca4f9efbd7cc649ff43b87970888f2812945b8 |
