Debian: CVE-2021-47506: linux -- security update

Debian: CVE-2021-47506: linux -- security update

Severity

7

CVSS

(AV:L/AC:L/Au:S/C:C/I:C/A:C)

Published

05/24/2024

Created

07/31/2024

Added

07/30/2024

Modified

01/30/2025

Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: fix use-after-free due to delegation race A delegation break could arrive as soon as we've called vfs_setlease.A delegation break runs a callback which immediately (in nfsd4_cb_recall_prepare) adds the delegation to del_recall_lru.If we then exit nfs4_set_delegation without hashing the delegation, it will be freed as soon as the callback is done with it, without ever being removed from del_recall_lru. Symptoms show up later as use-after-free or list corruption warnings, usually in the laundromat thread. I suspect aba2072f4523 "nfsd: grant read delegations to clients holding writes" made this bug easier to hit, but I looked as far back as v3.0 and it looks to me it already had the same problem.So I'm not sure where the bug was introduced; it may have been there from the beginning.

Solution(s)

• debian-upgrade-linux

References

• https://attackerkb.com/topics/cve-2021-47506
• CVE - 2021-47506