CVE-2026-89630

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

smb: client: restore the data offset bound in is valid oplock break()

Commit 83bfbd0bb902 ("cifs: Remove the RFC1002 header from smb hdr") changed the quantity this bound is measured against. It used to be srv->total read minus the 4-byte RFC1002 preamble that total read then included, so it was the SMB message length. The same commit stopped counting the preamble, and the mechanical substitution to srv->total read - srv->pdu size left an expression that is identically zero: standard receive3() reads MID HEADER SIZE() bytes and then exactly pdu length - MID HEADER SIZE() more, adding both to total read.

len is therefore 0, the subtraction below it wraps, and no u32 DataOffset can exceed the result, so the check from commit 097f5863b1a0 ("cifs: read overflow in is valid oplock break()") no longer rejects anything. Use total read, which is now the message length on its own.