CVE-2026-31403

Summary

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.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/76740c28050dc6db2f5550f1325b00a11bbb3255
• https://git.kernel.org/stable/c/c7f406fb341d6747634b8b1fa5461656e5e56076
• https://git.kernel.org/stable/c/d1a19217995df9c7e4118f5a2820c5032fef2945
• https://git.kernel.org/stable/c/e3d77f935639e6ae4b381c80464c31df998d61f4
• https://git.kernel.org/stable/c/db4a9f99b12a7ee1c19d86c83a3b752c7effa6c6
• https://git.kernel.org/stable/c/6a8d70e2ad6aad2c345a5048edcb8168036f97d6
• https://git.kernel.org/stable/c/e7fcf179b82d3a3730fd8615da01b087cc654d0b

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