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CVE-2021-47505— aio: fix use-after-free due to missing POLLFREE handling

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel 存在安全漏洞，该漏洞源于 aio 模块由于缺少 POLLFREE 处理而导致的释放后重用问题。

CVSS 7.8 · High EPSS 0.25% · P16

Affected Version Matrix 12

VendorProduct Version RangeStatus
Linux Linux 2c14fa838cbefc23cf1c73ca167ed85b274b2913< 321fba81ec034f88aea4898993c1bf15605c023f affected
2c14fa838cbefc23cf1c73ca167ed85b274b2913< 4105e6a128e8a98455dfc9e6dbb2ab0c33c4497f affected
2c14fa838cbefc23cf1c73ca167ed85b274b2913< 47ffefd88abfffe8a040bcc1dd0554d4ea6f7689 affected
2c14fa838cbefc23cf1c73ca167ed85b274b2913< 60d311f9e6381d779d7d53371f87285698ecee24 affected
2c14fa838cbefc23cf1c73ca167ed85b274b2913< 50252e4b5e989ce64555c7aef7516bdefc2fea72 affected
4.18 affected
< 4.18 unaffected
4.19.221≤ 4.19.* unaffected
… +4 more rows
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I. Basic Information for CVE-2021-47505

Vulnerability Information
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Vulnerability Title
aio: fix use-after-free due to missing POLLFREE handling
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: aio: fix use-after-free due to missing POLLFREE handling signalfd_poll() and binder_poll() are special in that they use a waitqueue whose lifetime is the current task, rather than the struct file as is normally the case. This is okay for blocking polls, since a blocking poll occurs within one task; however, non-blocking polls require another solution. This solution is for the queue to be cleared before it is freed, by sending a POLLFREE notification to all waiters. Unfortunately, only eventpoll handles POLLFREE. A second type of non-blocking poll, aio poll, was added in kernel v4.18, and it doesn't handle POLLFREE. This allows a use-after-free to occur if a signalfd or binder fd is polled with aio poll, and the waitqueue gets freed. Fix this by making aio poll handle POLLFREE. A patch by Ramji Jiyani <ramjiyani@google.com> (https://lore.kernel.org/r/20211027011834.2497484-1-ramjiyani@google.com) tried to do this by making aio_poll_wake() always complete the request inline if POLLFREE is seen. However, that solution had two bugs. First, it introduced a deadlock, as it unconditionally locked the aio context while holding the waitqueue lock, which inverts the normal locking order. Second, it didn't consider that POLLFREE notifications are missed while the request has been temporarily de-queued. The second problem was solved by my previous patch. This patch then properly fixes the use-after-free by handling POLLFREE in a deadlock-free way. It does this by taking advantage of the fact that freeing of the waitqueue is RCU-delayed, similar to what eventpoll does.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel 存在安全漏洞，该漏洞源于 aio 模块由于缺少 POLLFREE 处理而导致的释放后重用问题。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 2c14fa838cbefc23cf1c73ca167ed85b274b2913 ~ 321fba81ec034f88aea4898993c1bf15605c023f -
Linux Linux 4.18 -

II. Public POCs for CVE-2021-47505

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III. Intelligence Information for CVE-2021-47505

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Other References for CVE-2021-47505 (5)

Same Patch Batch · Linux · 2024-05-24 · 72 CVEs total

CVE-2021-47544 9.8 CRITICAL tcp: fix page frag corruption on page fault
CVE-2021-47536 9.8 CRITICAL net/smc: fix wrong list_del in smc_lgr_cleanup_early
CVE-2021-47506 9.8 CRITICAL nfsd: fix use-after-free due to delegation race
CVE-2021-47520 8.8 HIGH can: pch_can: pch_can_rx_normal: fix use after free
CVE-2021-47535 7.8 HIGH drm/msm/a6xx: Allocate enough space for GMU registers
CVE-2021-47533 7.8 HIGH drm/vc4: kms: Clear the HVS FIFO commit pointer once done
CVE-2021-47500 7.8 HIGH iio: mma8452: Fix trigger reference couting
CVE-2021-47552 7.8 HIGH blk-mq: cancel blk-mq dispatch work in both blk_cleanup_queue and disk_release()
CVE-2021-47551 7.8 HIGH drm/amd/amdkfd: Fix kernel panic when reset failed and been triggered again
CVE-2021-47555 7.8 HIGH net: vlan: fix underflow for the real_dev refcnt
CVE-2021-47541 7.8 HIGH net/mlx4_en: Fix an use-after-free bug in mlx4_en_try_alloc_resources()
CVE-2021-47561 7.8 HIGH i2c: virtio: disable timeout handling
CVE-2021-47517 7.8 HIGH ethtool: do not perform operations on net devices being unregistered
CVE-2023-52880 7.8 HIGH tty: n_gsm: require CAP_NET_ADMIN to attach N_GSM0710 ldisc
CVE-2021-47512 7.8 HIGH net/sched: fq_pie: prevent dismantle issue
CVE-2021-47502 7.8 HIGH ASoC: codecs: wcd934x: handle channel mappping list correctly
CVE-2021-47515 7.5 HIGH seg6: fix the iif in the IPv6 socket control block
CVE-2021-47559 7.5 HIGH net/smc: Fix NULL pointer dereferencing in smc_vlan_by_tcpsk()
CVE-2021-47549 sata_fsl: fix UAF in sata_fsl_port_stop when rmmod sata_fsl
CVE-2021-47569 io_uring: fail cancellation for EXITING tasks

Showing top 20 of 72 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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