CVE-2021-47506

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.

• linux linux kernel (< 4.4.296) • linux linux kernel (>= 4.5 < 4.9.294) • linux linux kernel (>= 4.10 < 4.14.259) • linux linux kernel (>= 4.15 < 4.19.222) • linux linux kernel (>= 4.20 < 5.4.168) • linux linux kernel (>= 5.5 < 5.10.85) • linux linux kernel (>= 5.11 < 5.15.8) • linux linux kernel 5.15