CVE-2026-53391

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

NFSv4/pNFS: reject zero-length raddr in nfs4decodempds_addr

nfs4decodempdsaddr() decodes the rnetid and raddr opaques of a netaddr4 from a GETDEVICEINFO multipath-DS body, then immediately calls strrchr(buf, '.') to locate the port separator. Both decodes use xdrstreamdecodestringdup(), and the current code checks only "nlen < 0" / "rlen < 0" before dereferencing the returned string.

When the on-wire opaque has length zero, xdrstreamdecodeopaqueinline() returns 0 and xdrstreamdecodestringdup() 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.