CVE-2021-47506 Information

May 25, 2024 cve

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 fsd: 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.

Reference

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