CVE-2026-90149NFSv4/flexfiles: fix NULL dereference for NFSv4.0 data servers

Official description

In the Linux kernel, the following vulnerability has been resolved: NFSv4/flexfiles: fix NULL dereference for NFSv4.0 data servers flexfiles accepts NFSv4.0 data servers, but two NFSv4 code paths assume the data server client has a session. Unlike NFSv4.1+, an NFSv4.0 client has no session (clp->cl_session is NULL; it uses clp->cl_slot_tbl), so I/O to a v4.0 flexfiles DS oopses: - nfs4_init_ds_session() dereferences clp->cl_session->session_state while seeding the DS lease. It also only seeds cl_lease_time when NFS4_SESSION_INITING is set; without a session that never happens, so cl_lease_time stays 0 and nfs4_renew_state() busy-loops, requeuing every 5 seconds. Seed the lease whenever there is no session and return before touching session state. - ff_layout_async_handle_error_v4() dereferences clp->cl_session->fc_slot_table on every DS I/O error. Fall back to the v4.0 transport slot table (clp->cl_slot_tbl) when there is no session.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/e55d7fec8a9290f73032ee34c35dd68532809633
• https://git.kernel.org/stable/c/336b6da10021c69a8f273bbacdf7432fdc89a06f
• https://git.kernel.org/stable/c/5527af72b0100c94287bfec901b6313eeac567ca
• https://git.kernel.org/stable/c/163c16e01f53fc8eb8d0f3484ae6c382265ecbbd
• https://git.kernel.org/stable/c/436a214514e24103159aea455147d58b44a8a585
• https://git.kernel.org/stable/c/2b03ebbf8d5e8f6af4ecd6c65375232dd1ec32cc