CVE-2021-47646

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 lastbfqqcreated 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

References

Affected packages

Git /

Affected ranges

Database specific

unresolved_ranges

[
    {
        "events": [
            {
                "introduced": "0"
            },
            {
                "fixed": "4.19.238"
            }
        ]
    },
    {
        "events": [
            {
                "introduced": "4.20"
            },
            {
                "fixed": "5.4.189"
            }
        ]
    },
    {
        "events": [
            {
                "introduced": "5.5"
            },
            {
                "fixed": "5.10.110"
            }
        ]
    },
    {
        "events": [
            {
                "introduced": "5.11"
            },
            {
                "fixed": "5.15.33"
            }
        ]
    },
    {
        "events": [
            {
                "introduced": "5.16"
            },
            {
                "fixed": "5.16.19"
            }
        ]
    },
    {
        "events": [
            {
                "introduced": "5.17"
            },
            {
                "fixed": "5.17.2"
            }
        ]
    }
]

source

"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-47646.json"