CVE-2021-47026: linux kernel Use-After-Free — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: RDMA/rtrs-clt: destroy sysfs after removing session from active list A session can be removed dynamically by sysfs interface "remove_path" that eventually calls rtrs_clt_remove_path_from_sysfs function. The current rtrs_clt_remove_path_from_sysfs first removes the sysfs interfaces and frees sess->stats object. Second it removes the session from the active list. Therefore some functions could access non-connected session and access the freed sess->stats object even-if they check the session status before accessing the session. For instance rtrs_clt_request and get_next_path_min_inflight check the session status and try to send IO to the session. The session status could be changed when they are trying to send IO but they could not catch the change and update the statistics information in sess->stats object, and generate use-after-free problem. (see: "RDMA/rtrs-clt: Check state of the rtrs_clt_sess before reading its stats") This patch changes the rtrs_clt_remove_path_from_sysfs to remove the session from the active session list and then destroy the sysfs interfaces. Each function still should check the session status because closing or error recovery paths can change the status.

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CVSS v3.1 Score

7.8

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness Type (CWE)

CWE-416 Use After Free

Affected Products

Vendor	Product	Versions
linux	linux_kernel	5.8 — 5.10.37
linux	linux_kernel	5.11 — 5.11.21
linux	linux_kernel	5.12 — 5.12.4

References

Advisories & Patches

https://git.kernel.org/stable/c/676171f9405dcaa45a33d18241c32f387dbaae39 https://git.kernel.org/stable/c/7f4a8592ff29f19c5a2ca549d0973821319afaad https://git.kernel.org/stable/c/b64415c6b3476cf9fa4d0aea3807065b8403a937 https://git.kernel.org/stable/c/d3cca8067d43dfee4a3535c645b55f618708dccb https://git.kernel.org/stable/c/676171f9405dcaa45a33d18241c32f387dbaae39 https://git.kernel.org/stable/c/7f4a8592ff29f19c5a2ca549d0973821319afaad https://git.kernel.org/stable/c/b64415c6b3476cf9fa4d0aea3807065b8403a937 https://git.kernel.org/stable/c/d3cca8067d43dfee4a3535c645b55f618708dccb

Frequently Asked Questions

What is CVE-2021-47026? +

In the Linux kernel, the following vulnerability has been resolved: RDMA/rtrs-clt: destroy sysfs after removing session from active list A session can be removed dynamically by sysfs interface "remove_path" that eventually calls rtrs_clt_remove_path_from_sysfs function. The current rtrs_clt_remove_path_from_sysfs first removes the sysfs interfaces and frees sess->stats object. Second it removes the session from the active list. Therefore some functions could access non-connected session and access the freed sess->stats object even-if they check the session status before accessing the session. For instance rtrs_clt_request and get_next_path_min_inflight check the session status and try to send IO to the session. The session status could be changed when they are trying to send IO but they could not catch the change and update the statistics information in sess->stats object, and generate use-after-free problem. (see: "RDMA/rtrs-clt: Check state of the rtrs_clt_sess before reading its stats") This patch changes the rtrs_clt_remove_path_from_sysfs to remove the session from the active session list and then destroy the sysfs interfaces. Each function still should check the session status because closing or error recovery paths can change the status. It has a CVSS v3.1 base score of 7.8 (HIGH).

How severe is CVE-2021-47026? +

CVE-2021-47026 has a CVSS v3.1 score of 7.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2021-47026? +

CVE-2021-47026 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2021-47026? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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