CVE-2021-47254

HIGH
Published May 21, 2024 Modified Mar 17, 2026 CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: gfs2: Fix use-after-free in gfs2_glock_shrink_scan The GLF_LRU flag is checked under lru_lock in gfs2_glock_remove_from_lru() to remove the glock from the lru list in __gfs2_glock_put(). On the shrink scan path, the same flag is cleared under lru_lock but because of cond_resched_lock(&lru_lock) in gfs2_dispose_glock_lru(), progress on the put side can be made without deleting the glock from the lru list. Keep GLF_LRU across the race window opened by cond_resched_lock(&lru_lock) to ensure correct behavior on both sides - clear GLF_LRU after list_del under lru_lock.

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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
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel

References

Advisories & Patches

https://git.kernel.org/stable/c/0364742decb0f02bc183404868b82896f7992595 https://git.kernel.org/stable/c/094bf5670e762afa243d2c41a5c4ab71c7447bf4 https://git.kernel.org/stable/c/1ab19c5de4c537ec0d9b21020395a5b5a6c059b2 https://git.kernel.org/stable/c/38ce329534500bf4ae71f81df6a37a406cf187b4 https://git.kernel.org/stable/c/86fd5b27db743a0ce0cc245e3a34813b2aa6ec1d https://git.kernel.org/stable/c/92869945cc5b78ee8a1ef90336fe070893e3458a https://git.kernel.org/stable/c/a61156314b66456ab6a291ed5deba1ebd002ab3c https://git.kernel.org/stable/c/e87ef30fe73e7e10d2c85bdcc778dcec24dca553 https://git.kernel.org/stable/c/0364742decb0f02bc183404868b82896f7992595 https://git.kernel.org/stable/c/094bf5670e762afa243d2c41a5c4ab71c7447bf4 https://git.kernel.org/stable/c/1ab19c5de4c537ec0d9b21020395a5b5a6c059b2 https://git.kernel.org/stable/c/38ce329534500bf4ae71f81df6a37a406cf187b4 https://git.kernel.org/stable/c/86fd5b27db743a0ce0cc245e3a34813b2aa6ec1d https://git.kernel.org/stable/c/92869945cc5b78ee8a1ef90336fe070893e3458a https://git.kernel.org/stable/c/a61156314b66456ab6a291ed5deba1ebd002ab3c https://git.kernel.org/stable/c/e87ef30fe73e7e10d2c85bdcc778dcec24dca553

Frequently Asked Questions

What is CVE-2021-47254? +
In the Linux kernel, the following vulnerability has been resolved: gfs2: Fix use-after-free in gfs2_glock_shrink_scan The GLF_LRU flag is checked under lru_lock in gfs2_glock_remove_from_lru() to remove the glock from the lru list in __gfs2_glock_put(). On the shrink scan path, the same flag is cleared under lru_lock but because of cond_resched_lock(&lru_lock) in gfs2_dispose_glock_lru(), progress on the put side can be made without deleting the glock from the lru list. Keep GLF_LRU across the race window opened by cond_resched_lock(&lru_lock) to ensure correct behavior on both sides - clear GLF_LRU after list_del under lru_lock. It has a CVSS v3.1 base score of 7.8 (HIGH).
How severe is CVE-2021-47254? +
CVE-2021-47254 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-2021-47254? +
CVE-2021-47254 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-2021-47254? +
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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