CVE-2021-47107

Summary

In the Linux kernel, the following vulnerability has been resolved:

NFSD: Fix READDIR buffer overflow

If a client sends a READDIR count argument that is too small (say, zero), then the buffer size calculation in the new init_dirlist helper functions results in an underflow, allowing the XDR stream functions to write beyond the actual buffer.

This calculation has always been suspect. NFSD has never sanity- checked the READDIR count argument, but the old entry encoders managed the problem correctly.

With the commits below, entry encoding changed, exposing the underflow to the pointer arithmetic in xdr_reserve_space().

Modern NFS clients attempt to retrieve as much data as possible for each READDIR request. Also, we have no unit tests that exercise the behavior of READDIR at the lower bound of @count values. Thus this case was missed during testing.

Affected Software

VendorProductVersion RangeStatus
LinuxLinux37aa5e64022243e721b8334122997881177a4cfc < 9e291a6a28d32545ed2fd959a8165144d1724df1affected
LinuxLinux7f87fc2d34d475225e78b7f5c4eabb121f4282b2 < eabc0aab98e5218ceecd82069b0d6fdfff5ee885affected
LinuxLinux7f87fc2d34d475225e78b7f5c4eabb121f4282b2 < 53b1119a6e5028b125f431a0116ba73510d82a72affected
LinuxLinux5.13affected
LinuxLinux0 < 5.13unaffected
LinuxLinux5.15.12 <= 5.15.*unaffected
LinuxLinux5.16 <= *unaffected

Weaknesses

ADP Enrichment

CISA ADP Vulnrichment

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

CVE Program Container

Additional References

Additional References

References