CVE-2026-89671

Published: September 15, 2026Last modified: September 28, 2026

Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: gate nfs3 setacl by argp->mask nfsd3_proc_setacl() calls set_posix_acl() unconditionally for both ACL_TYPE_ACCESS and ACL_TYPE_DEFAULT, passing argp->acl_access and argp->acl_default verbatim. The NFSv3 ACL decoder only populates those pointers when the corresponding mask bit is set: nfs3svc_decode_setaclargs() if (args->mask & NFS_ACL) decode into acl_access if (args->mask & NFS_DFACL) decode into acl_default /* otherwise the pointer stays NULL (pc_argzero) */ nfsd3_proc_setacl() set_posix_acl(.., ACL_TYPE_ACCESS, argp->acl_access) set_posix_acl(.., ACL_TYPE_DEFAULT, argp->acl_default) set_posix_acl(idmap, dentry, type, NULL) is the VFS "remove this ACL type" operation. A NULL pointer that means "the client did not send this arm" is therefore indistinguishable from "the client asked to remove this ACL". A SETACL with mask=NFS_ACL silently drops the directory's default ACL; mask=0 drops both. The sibling nfsd3_proc_getacl() already consults argp->mask before touching each arm; mirror that in setacl. Fix by wrapping each set_posix_acl() call in the matching mask bit check and initializing error to 0 before inode_lock so that a request with neither bit set leaves the on-disk ACLs untouched and returns nfs_ok. The out_drop_lock path and the unconditional posix_acl_release() at out: are preserved; both NULL-tolerate the skipped arms.

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References

• https://git.kernel.org/stable/c/3be1d8611dae4829e4608007db29f4a8748c37b2
• https://git.kernel.org/stable/c/453d7198a0ab07a12d46e0575861ac7b932da17e
• https://git.kernel.org/stable/c/68a80b26efdff1d09f8ae1773c6a915abb9e191d
• https://git.kernel.org/stable/c/b3bff820d068ea59767d4e91a3258231a879da5f
• https://git.kernel.org/stable/c/ff99ed007f065198fd723152405c22aa558f700b