Re: [PATCH 11/39] selinux: reject writable opens of policy file, drop mmap shared/write check
From: sashiko-bot@kernel.org
Date: 2026-09-08 20:36:18
Also in:
bpf, dri-devel, kvm, kvmarm, linux-perf-users, 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. 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/20260908-b4-mmap-prepare-vma-flag-sanify-v1-0-dacf19cce22b@kernel.org?part=11