| 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-2024-35929: rcu/nocb: Fix WARN_ON_ONCE() in the rcu_nocb_bypass_lock() |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| rcu/nocb: Fix WARN_ON_ONCE() in the rcu_nocb_bypass_lock() |
| |
| For the kernels built with CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y and |
| CONFIG_RCU_LAZY=y, the following scenarios will trigger WARN_ON_ONCE() |
| in the rcu_nocb_bypass_lock() and rcu_nocb_wait_contended() functions: |
| |
| CPU2 CPU11 |
| kthread |
| rcu_nocb_cb_kthread ksys_write |
| rcu_do_batch vfs_write |
| rcu_torture_timer_cb proc_sys_write |
| __kmem_cache_free proc_sys_call_handler |
| kmemleak_free drop_caches_sysctl_handler |
| delete_object_full drop_slab |
| __delete_object shrink_slab |
| put_object lazy_rcu_shrink_scan |
| call_rcu rcu_nocb_flush_bypass |
| __call_rcu_commn rcu_nocb_bypass_lock |
| raw_spin_trylock(&rdp->nocb_bypass_lock) fail |
| atomic_inc(&rdp->nocb_lock_contended); |
| rcu_nocb_wait_contended WARN_ON_ONCE(smp_processor_id() != rdp->cpu); |
| WARN_ON_ONCE(atomic_read(&rdp->nocb_lock_contended)) | |
| |_ _ _ _ _ _ _ _ _ _same rdp and rdp->cpu != 11_ _ _ _ _ _ _ _ _ __| |
| |
| Reproduce this bug with "echo 3 > /proc/sys/vm/drop_caches". |
| |
| This commit therefore uses rcu_nocb_try_flush_bypass() instead of |
| rcu_nocb_flush_bypass() in lazy_rcu_shrink_scan(). If the nocb_bypass |
| queue is being flushed, then rcu_nocb_try_flush_bypass will return |
| directly. |
| |
| The Linux kernel CVE team has assigned CVE-2024-35929 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Fixed in 6.6.27 with commit 4d58c9fb45c70e62c19e8be3f3605889c47601bc |
| Fixed in 6.8.6 with commit 927d1f4f77e4784ab3944a9df86ab14d1cd3185a |
| Fixed in 6.9 with commit dda98810b552fc6bf650f4270edeebdc2f28bd3f |
| |
| 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-2024-35929 |
| 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/rcu/tree_nocb.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/4d58c9fb45c70e62c19e8be3f3605889c47601bc |
| https://git.kernel.org/stable/c/927d1f4f77e4784ab3944a9df86ab14d1cd3185a |
| https://git.kernel.org/stable/c/dda98810b552fc6bf650f4270edeebdc2f28bd3f |
