CVE-2021-47646

Revert "Revert "block, bfq: honor already-setup queue merges""

HIGH

7.8

CVSS Score

Published: February 26, 2025 at 01:54 AM UTC

Updated: August 11, 2026 at 03:37 AM UTC

1 product affected across 1 vendorLinux Kernel

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Severity

HIGH7.8

Exploit prediction

EPSS 0.3%

SSVC

No known exploit

Description

In the Linux kernel, the following vulnerability has been resolved: Revert "Revert "block, bfq: honor already-setup queue merges"" A crash [1] happened to be triggered in conjunction with commit 2d52c58b9c9b ("block, bfq: honor already-setup queue merges"). The latter was then reverted by commit ebc69e897e17 ("Revert "block, bfq: honor already-setup queue merges""). Yet, the reverted commit was not the one introducing the bug. In fact, it actually triggered a UAF introduced by a different commit, and now fixed by commit d29bd41428cf ("block, bfq: reset last_bfqq_created on group change"). So, there is no point in keeping commit 2d52c58b9c9b ("block, bfq: honor already-setup queue merges") out. This commit restores it. [1] https://bugzilla.kernel.org/show_bug.cgi?id=214503

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Linux Kernel · Linux

95%

v < 4.19.2384.20 ≤ v < 5.4.1895.11 ≤ v < 5.15.335.13 ≤ v < 5.15.335.13 ≤ v < 5.16.195.13 ≤ v < 5.17.25.13 ≤ v < 5.185.16 ≤ v < 5.16.195.17 ≤ v < 5.17.25.5 ≤ v < 5.10.110430a67f9d6169a7b3e328bceb2ef9542e4153c7c5.13

Vendor states this is fixed in 15729ff8143f8135b03988a100a19e66d7cb7ecd (fixed)

Vendor states this is fixed in 4083925bd6dc89216d156474a8076feec904e607 (fixed)

Vendor states this is fixed in 65d8a737452e88f251fe5d925371de6d606df613 (fixed)

Vendor states this is fixed in abc2129e646af7b43025d90a071f83043f1ae76c (fixed)

Affected range stops below 4.19.238, so it looks safe — our inference, not a vendor statement

Affected range stops below 5.10.110, so it looks safe — our inference, not a vendor statement

Vendor states this is fixed in 5.13 (unaffected)

Vendor states this is fixed in 5.15.33 (unaffected)

Vendor states this is fixed in 5.16.19 (unaffected)

Vendor states this is fixed in 5.17.2 (unaffected)

Vendor states this is fixed in 5.18 (unaffected)

Affected range stops below 5.4.189, so it looks safe — our inference, not a vendor statement