Description (CNA)
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.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 07ec77a1d4e82526e1588979fff2f024f8e96df2 before b22faa21b6230d5eccd233e1b7e0026a5002b287; affected 07ec77a1d4e82526e1588979fff2f024f8e96df2 before 7b5cc7fd1789ea5dbb942c9f8207b076d365badc; affected 07ec77a1d4e82526e1588979fff2f024f8e96df2 before 87ca4f9efbd7cc649ff43b87970888f2812945b8 |
| Linux / Linux | affected 5.15; unaffected 0 before 5.15; unaffected 5.15.89 through 5.15.*; unaffected 6.1.7 through 6.1.*; unaffected 6.2 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/b22faa21b6230d5eccd233e1b7e0026a5002b287
- https://git.kernel.org/stable/c/7b5cc7fd1789ea5dbb942c9f8207b076d365badc
- https://git.kernel.org/stable/c/87ca4f9efbd7cc649ff43b87970888f2812945b8
ADP enrichment
No English description supplied.
No references supplied.