linux/security
Paul Moore 6af36aeb14 lsm: add backing_file LSM hooks
Stacked filesystems such as overlayfs do not currently provide the
necessary mechanisms for LSMs to properly enforce access controls on the
mmap() and mprotect() operations.  In order to resolve this gap, a LSM
security blob is being added to the backing_file struct and the following
new LSM hooks are being created:

 security_backing_file_alloc()
 security_backing_file_free()
 security_mmap_backing_file()

The first two hooks are to manage the lifecycle of the LSM security blob
in the backing_file struct, while the third provides a new mmap() access
control point for the underlying backing file.  It is also expected that
LSMs will likely want to update their security_file_mprotect() callback
to address issues with their mprotect() controls, but that does not
require a change to the security_file_mprotect() LSM hook.

There are a three other small changes to support these new LSM hooks:
* Pass the user file associated with a backing file down to
alloc_empty_backing_file() so it can be included in the
security_backing_file_alloc() hook.
* Add getter and setter functions for the backing_file struct LSM blob
as the backing_file struct remains private to fs/file_table.c.
* Constify the file struct field in the LSM common_audit_data struct to
better support LSMs that need to pass a const file struct pointer into
the common LSM audit code.

Thanks to Arnd Bergmann for identifying the missing EXPORT_SYMBOL_GPL()
and supplying a fixup.

Cc: stable@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-unionfs@vger.kernel.org
Cc: linux-erofs@lists.ozlabs.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Paul Moore <paul@paul-moore.com>
2026-04-03 16:53:50 -04:00
..
apparmor Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
bpf lsm: replace the name field with a pointer to the lsm_id struct 2025-10-22 19:24:18 -04:00
integrity Convert remaining multi-line kmalloc_obj/flex GFP_KERNEL uses 2026-02-22 08:26:33 -08:00
ipe Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
keys Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
landlock Convert 'alloc_flex' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
loadpin Convert 'alloc_flex' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
lockdown lockdown: move initcalls to the LSM framework 2025-10-22 19:24:27 -04:00
safesetid Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
selinux Convert remaining multi-line kmalloc_obj/flex GFP_KERNEL uses 2026-02-22 08:26:33 -08:00
smack Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
tomoyo treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
yama Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
commoncap_test.c security: Add KUnit tests for kuid_root_in_ns and vfsuid_root_in_currentns 2026-01-09 11:28:28 -06:00
commoncap.c security: Add KUnit tests for kuid_root_in_ns and vfsuid_root_in_currentns 2026-01-09 11:28:28 -06:00
device_cgroup.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
inode.c securityfs: use kstrdup_const() to manage symlink targets 2026-03-17 17:13:36 -04:00
Kconfig security: Add KUnit tests for kuid_root_in_ns and vfsuid_root_in_currentns 2026-01-09 11:28:28 -06:00
Kconfig.hardening rust: add bitmap API. 2025-09-22 15:52:44 -04:00
lsm_audit.c net: Retire DCCP socket. 2025-04-11 18:58:10 -07:00
lsm_init.c lsm: add backing_file LSM hooks 2026-04-03 16:53:50 -04:00
lsm_notifier.c lsm: split the notifier code out into lsm_notifier.c 2025-10-22 19:24:15 -04:00
lsm_syscalls.c lsm: rework lsm_active_cnt and lsm_idlist[] 2025-10-22 19:24:19 -04:00
lsm.h lsm: add backing_file LSM hooks 2026-04-03 16:53:50 -04:00
Makefile lsm: split the init code out into lsm_init.c 2025-10-22 19:24:16 -04:00
min_addr.c lsm: preserve /proc/sys/vm/mmap_min_addr when !CONFIG_SECURITY 2026-01-29 13:56:53 -05:00
security.c lsm: add backing_file LSM hooks 2026-04-03 16:53:50 -04:00