CVE-2026-53391NFSv4/pNFS: reject zero-length r_addr in nfs4_decode_mp_ds_addr

Official description

In the Linux kernel, the following vulnerability has been resolved: NFSv4/pNFS: reject zero-length r_addr in nfs4_decode_mp_ds_addr nfs4_decode_mp_ds_addr() decodes the r_netid and r_addr opaques of a netaddr4 from a GETDEVICEINFO multipath-DS body, then immediately calls strrchr(buf, '.') to locate the port separator. Both decodes use xdr_stream_decode_string_dup(), and the current code checks only "nlen < 0" / "rlen < 0" before dereferencing the returned string. When the on-wire opaque has length zero, xdr_stream_decode_opaque_inline() returns 0 and xdr_stream_decode_string_dup() falls through to its "*str = NULL; return ret" tail, leaving buf NULL with a return value of 0. The "< 0" check does not catch this, and the next line is strrchr(NULL, '.'), a kernel NULL pointer dereference reachable from any pNFS-flexfile client mounted against a malicious or compromised metadata server. Reject the zero-length cases explicitly so the decoder fails with -EBADMSG (treated as a malformed GETDEVICEINFO body) instead of panicking the client.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/76b94cbd32aacf36a641956385a852635c6802b9
• https://git.kernel.org/stable/c/c8e4e0c701d0192a2efb6df059c0f9e19678c23d
• https://git.kernel.org/stable/c/6c344fff2feff9d4d716d8e4ad40e9b5040ee5ea
• https://git.kernel.org/stable/c/427ab81a811dab4bca9d19f82eec5847ae42646e
• https://git.kernel.org/stable/c/012d37a568bfbb2c9686f03ade75560bc7139956
• https://git.kernel.org/stable/c/30aae62e50b4e074a90a9a5e15246548fbdc1182
• https://git.kernel.org/stable/c/41fe0f7b84f0cb822ae10ab08592996a592b2a25