CVE-2026-31403

Description

In the Linux kernel, the following vulnerability has been resolved: NFSD: Hold net reference for the lifetime of /proc/fs/nfs/exports fd The /proc/fs/nfs/exports proc entry is created at module init and persists for the module's lifetime. exports_proc_open() captures the caller's current network namespace and stores its svc_export_cache in seq->private, but takes no reference on the namespace. If the namespace is subsequently torn down (e.g. container destruction after the opener does setns() to a different namespace), nfsd_net_exit() calls nfsd_export_shutdown() which frees the cache. Subsequent reads on the still-open fd dereference the freed cache_detail, walking a freed hash table. Hold a reference on the struct net for the lifetime of the open file descriptor. This prevents nfsd_net_exit() from running -- and thus prevents nfsd_export_shutdown() from freeing the cache -- while any exports fd is open. cache_detail already stores its net pointer (cd->net, set by cache_create_net()), so exports_release() can retrieve it without additional per-file storage.

References

• https://git.kernel.org/stable/c/6a8d70e2ad6aad2c345a5048edcb8168036f97d6
• https://git.kernel.org/stable/c/c7f406fb341d6747634b8b1fa5461656e5e56076
• https://git.kernel.org/stable/c/d1a19217995df9c7e4118f5a2820c5032fef2945
• https://git.kernel.org/stable/c/db4a9f99b12a7ee1c19d86c83a3b752c7effa6c6
• https://git.kernel.org/stable/c/e3d77f935639e6ae4b381c80464c31df998d61f4