Linux Distros 未修补的漏洞: CVE-2021-46921
medium Nessus 插件 ID 224463
语言：
简介
Linux/Unix 主机上安装的一个或多个程序包存在漏洞，但供应商表示不会修补此漏洞。描述
Linux/Unix 主机中安装的一个或多个程序包受到一个漏洞影响，而供应商没有提供补丁程序。- 在 Linux 内核中，已解决以下漏洞： locking/qrwlock: Fix ordering in queued_write_lock_slowpath() While this code is executed with the wait_lock held, a reader can acquire the lock without holding wait_lock. The writer side loops checking the value with the atomic_cond_read_acquire(), but only truly acquires the lock when the compare-and-exchange is completed successfully which isn't ordered. This exposes the window between the acquire and the cmpxchg to an A-B-A problem which allows reads following the lock acquisition to observe values speculatively before the write lock is truly acquired. We've seen a problem in epoll where the reader does a xchg while holding the read lock, but the writer can see a value change out from under it. Writer | Reader
-------------------------------------------------------------------------------- ep_scan_ready_list() | |- write_lock_irq() | |- queued_write_lock_slowpath() | |- atomic_cond_read_acquire() | | read_lock_irqsave(&ep->lock, flags); --> (observes value before unlock) | chain_epi_lockless() | | epi->next = xchg(&ep->ovflist, epi); | | read_unlock_irqrestore(&ep->lock, flags); | | | atomic_cmpxchg_relaxed() | |-- READ_ONCE(ep->ovflist); | A core can order the read of the ovflist ahead of the atomic_cmpxchg_relaxed(). Switching the cmpxchg to use acquire semantics addresses this issue at which point the atomic_cond_read can be switched to use relaxed semantics. [peterz: use try_cmpxchg()] (CVE-2021-46921)
请注意，Nessus 依赖供应商报告的程序包是否存在进行判断。
解决方案
目前尚未有任何已知的解决方案。插件详情
严重性: Medium
ID: 224463
文件名: unpatched_CVE_2021_46921.nasl
版本: 1.1
类型: local
代理: unix
系列: Misc.
发布时间: 2025/3/5
最近更新时间: 2025/3/5
支持的传感器: Nessus Agent, Nessus
风险信息
VPR
风险因素: Medium
分数: 4.4
CVSS v2
风险因素: Medium
基本分数: 4.6
时间分数: 3.4
矢量: CVSS2#AV:L/AC:L/Au:S/C:C/I:N/A:N
CVSS 分数来源: CVE-2021-46921
CVSS v3
风险因素: Medium
基本分数: 5.5
时间分数: 4.8
矢量: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
时间矢量: CVSS:3.0/E:U/RL:O/RC:C
漏洞信息
必需的 KB 项: Host/local_checks_enabled, Host/cpu, global_settings/vendor_unpatched
易利用性: No known exploits are available
漏洞发布日期: 2024/2/27
参考资料信息
CVE: CVE-2021-46921