On Wed, Apr 29, 2026 at 8:03 PM Song Liu <[email protected]> wrote: > > Add six new LSM hooks for mount operations: > > - mount_bind(from, to, recurse): bind mount with pre-resolved > struct path for source and destination. > - mount_new(fc, mp, mnt_flags, flags, data): new mount, called after > mount options are parsed. The flags and data parameters carry the > original mount(2) flags and data for LSMs that need them (AppArmor, > Tomoyo). > - mount_remount(fc, mp, mnt_flags, flags, data): filesystem remount, > called after mount options are parsed into the fs_context. > - mount_reconfigure(mp, mnt_flags, flags): mount flag reconfiguration > (MS_REMOUNT|MS_BIND path). > - mount_move(from, to): move mount with pre-resolved paths. > - mount_change_type(mp, ms_flags): propagation type changes. > > These replace the monolithic security_sb_mount() which conflates > multiple distinct operations into a single hook, and suffers from > TOCTOU issues where LSMs re-resolve string-based dev_name via > kern_path(). > > The mount_move hook is added alongside the existing move_mount hook. > During the transition, LSMs register for both hooks. The move_mount > hook will be removed once all LSMs have been converted. > > Some LSMs, such as apparmor and tomoyo, audit the original input passed > in the mount syscall. To keep the same behavior, argument data and flags > are passed in do_* functions. These can be removed if these LSMs no > longer need these information. > > All new hooks are registered as sleepable BPF LSM hooks. > > Code generated with the assistance of Claude, reviewed by human. > > Reviewed-by: Stephen Smalley <[email protected]> > Tested-by: Stephen Smalley <[email protected]> # for selinux only > Signed-off-by: Song Liu <[email protected]> > --- > fs/namespace.c | 35 ++++++++++-- > include/linux/lsm_hook_defs.h | 12 ++++ > include/linux/security.h | 50 +++++++++++++++++ > kernel/bpf/bpf_lsm.c | 7 +++ > security/security.c | 101 ++++++++++++++++++++++++++++++++++ > 5 files changed, 199 insertions(+), 6 deletions(-)
... > @@ -3708,6 +3724,10 @@ static int do_move_mount_old(const struct path *path, > const char *old_name) > if (err) > return err; > > + err = security_mount_move(&old_path, path); > + if (err) > + return err; > + > return do_move_mount(&old_path, path, 0); > } While the security_sb_mount() hook calls into do_move_mount_old(), the security_move_mount() hook calls into do_mount_mount(). As you remove both of these LSM hooks in patch 7/7, should we consider moving the new security_mount_move() into do_move_mount()? If not, how do we ensure that we don't lose coverage when removing the security_move_mount() hook, or can you explain why it is not needed? -- paul-moore.com
