Re: [PATCH v3 12/40] selinux: reject writable opens of policy file, drop mmap shared/write check
From: sashiko-bot@kernel.org
Date: 2026-09-17 17:25:29
Also in:
bpf, dri-devel, kvm, kvmarm, linux-perf-users, linux-rdma, linux-s390, linux-scsi, selinux
The policy file has no write method and is exposed read-only (S_IRUGO in selinux_files[]), yet sel_open_policy() performs no open mode check, so a CAP_DAC_OVERRIDE caller can open it O_RDWR. Reject FMODE_WRITE at open, as kernfs does. The file can then never be mapped with FMODE_WRITE, so do_mmap() always clears VM_MAYWRITE and VM_SHARED for MAP_SHARED mappings and the VM_SHARED check in sel_mmap_policy() cannot be reached. Remove it. This also stops sel_mmap_policy() clearing VM_MAYWRITE on a mapping that is neither a PFN map nor a mixed map, ahead of the core enforcing that only such mappings may do so. Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com> Reviewed-by: Jann Horn <jannh@google.com> Acked-by: Paul Moore <paul@paul-moore.com> Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Sashiko has reviewed this patch and found no issues. It looks great! -- Sashiko AI review · https://sashiko.dev/#/patchset/20260917-b4-mmap-prepare-vma-flag-sanify-v3-0-4583d8a23bca@kernel.org?part=12