CVE-2021-47506

Summary

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.

Affected Software

VendorProductVersion RangeStatus
LinuxLinuxdff1399f8addf7129c49bb2227469da79cc30b47 < 04a8d07f3d58308b92630045560799a3faa3ebceaffected
LinuxLinuxdff1399f8addf7129c49bb2227469da79cc30b47 < 348714018139c39533c55661a0c7c990671396b4affected
LinuxLinuxdff1399f8addf7129c49bb2227469da79cc30b47 < 33645d3e22720cac1e4548f8fef57bf0649536eeaffected
LinuxLinuxdff1399f8addf7129c49bb2227469da79cc30b47 < 2becaa990b93cbd2928292c0b669d3abb6cf06d4affected
LinuxLinuxdff1399f8addf7129c49bb2227469da79cc30b47 < e0759696de6851d7536efddfdd2dfed4c4df1f09affected
LinuxLinuxdff1399f8addf7129c49bb2227469da79cc30b47 < eeb0711801f5e19ef654371b627682aed3b11373affected
LinuxLinuxdff1399f8addf7129c49bb2227469da79cc30b47 < 148c816f10fd11df27ca6a9b3238cdd42fa72cd3affected
LinuxLinuxdff1399f8addf7129c49bb2227469da79cc30b47 < 548ec0805c399c65ed66c6641be467f717833ab5affected
LinuxLinux3.17affected
LinuxLinux0 < 3.17unaffected
LinuxLinux4.4.296 <= 4.4.*unaffected
LinuxLinux4.9.294 <= 4.9.*unaffected
LinuxLinux4.14.259 <= 4.14.*unaffected
LinuxLinux4.19.222 <= 4.19.*unaffected
LinuxLinux5.4.168 <= 5.4.*unaffected
LinuxLinux5.10.85 <= 5.10.*unaffected
LinuxLinux5.15.8 <= 5.15.*unaffected
LinuxLinux5.16 <= *unaffected

Weaknesses

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: total

CVE Program Container

Additional References

References