CVE-2021-47004: linux kernel — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to avoid touching checkpointed data in get_victim() In CP disabling mode, there are two issues when using LFS or SSR | AT_SSR mode to select victim: 1. LFS is set to find source section during GC, the victim should have no checkpointed data, since after GC, section could not be set free for reuse. Previously, we only check valid chpt blocks in current segment rather than section, fix it. 2. SSR | AT_SSR are set to find target segment for writes which can be fully filled by checkpointed and newly written blocks, we should never select such segment, otherwise it can cause panic or data corruption during allocation, potential case is described as below: a) target segment has 'n' (n < 512) ckpt valid blocks b) GC migrates 'n' valid blocks to other segment (segment is still in dirty list) c) GC migrates '512 - n' blocks to target segment (segment has 'n' cp_vblocks and '512 - n' vblocks) d) If GC selects target segment via {AT,}SSR allocator, however there is no free space in targe segment.

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CVSS v3.1 Score

7.1

HIGH

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

Affected Products

Vendor	Product	Versions
linux	linux_kernel	4.20 — 5.10.38
linux	linux_kernel	5.11 — 5.11.22
linux	linux_kernel	5.12 — 5.12.5

References

Advisories & Patches

https://git.kernel.org/stable/c/105155a8146ddb54c119d8318964eef3859d109d https://git.kernel.org/stable/c/1e116f87825f01a6380286472196882746b16f63 https://git.kernel.org/stable/c/211372b2571520e394b56b431a0705586013b3ff https://git.kernel.org/stable/c/61461fc921b756ae16e64243f72af2bfc2e620db https://git.kernel.org/stable/c/105155a8146ddb54c119d8318964eef3859d109d https://git.kernel.org/stable/c/1e116f87825f01a6380286472196882746b16f63 https://git.kernel.org/stable/c/211372b2571520e394b56b431a0705586013b3ff https://git.kernel.org/stable/c/61461fc921b756ae16e64243f72af2bfc2e620db

Frequently Asked Questions

What is CVE-2021-47004? +

In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to avoid touching checkpointed data in get_victim() In CP disabling mode, there are two issues when using LFS or SSR | AT_SSR mode to select victim: 1. LFS is set to find source section during GC, the victim should have no checkpointed data, since after GC, section could not be set free for reuse. Previously, we only check valid chpt blocks in current segment rather than section, fix it. 2. SSR | AT_SSR are set to find target segment for writes which can be fully filled by checkpointed and newly written blocks, we should never select such segment, otherwise it can cause panic or data corruption during allocation, potential case is described as below: a) target segment has 'n' (n < 512) ckpt valid blocks b) GC migrates 'n' valid blocks to other segment (segment is still in dirty list) c) GC migrates '512 - n' blocks to target segment (segment has 'n' cp_vblocks and '512 - n' vblocks) d) If GC selects target segment via {AT,}SSR allocator, however there is no free space in targe segment. It has a CVSS v3.1 base score of 7.1 (HIGH).

How severe is CVE-2021-47004? +

CVE-2021-47004 has a CVSS v3.1 score of 7.1 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2021-47004? +

CVE-2021-47004 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-2021-47004? +

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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CVE-2021-47004