On Tue, Feb 02, 2021 at 05:27:04PM +0100, Mickaël Salaün wrote: > From: Mickaël Salaün <mic@xxxxxxxxxxxxxxxxxxx> > > The sb_delete security hook is called when shutting down a superblock, > which may be useful to release kernel objects tied to the superblock's > lifetime (e.g. inodes). > > This new hook is needed by Landlock to release (ephemerally) tagged > struct inodes. This comes from the unprivileged nature of Landlock > described in the next commit. > > Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > Cc: James Morris <jmorris@xxxxxxxxx> > Cc: Kees Cook <keescook@xxxxxxxxxxxx> > Cc: Serge E. Hallyn <serge@xxxxxxxxxx> One note below, but Acked-by: Serge Hallyn <serge@xxxxxxxxxx> > Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxxxxxxxxxx> > Reviewed-by: Jann Horn <jannh@xxxxxxxxxx> > --- > > Changes since v22: > * Add Reviewed-by: Jann Horn <jannh@xxxxxxxxxx> > > Changes since v17: > * Initial patch to replace the direct call to landlock_release_inodes() > (requested by James Morris). > https://lore.kernel.org/lkml/alpine.LRH.2.21.2005150536440.7929@xxxxxxxxx/ > --- > fs/super.c | 1 + > include/linux/lsm_hook_defs.h | 1 + > include/linux/lsm_hooks.h | 2 ++ > include/linux/security.h | 4 ++++ > security/security.c | 5 +++++ > 5 files changed, 13 insertions(+) > > diff --git a/fs/super.c b/fs/super.c > index 2c6cdea2ab2d..c3c5178cde65 100644 > --- a/fs/super.c > +++ b/fs/super.c > @@ -454,6 +454,7 @@ void generic_shutdown_super(struct super_block *sb) > evict_inodes(sb); > /* only nonzero refcount inodes can have marks */ > fsnotify_sb_delete(sb); > + security_sb_delete(sb); > > if (sb->s_dio_done_wq) { > destroy_workqueue(sb->s_dio_done_wq); > diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h > index 7aaa753b8608..32472b3849bc 100644 > --- a/include/linux/lsm_hook_defs.h > +++ b/include/linux/lsm_hook_defs.h > @@ -59,6 +59,7 @@ LSM_HOOK(int, 0, fs_context_dup, struct fs_context *fc, > LSM_HOOK(int, -ENOPARAM, fs_context_parse_param, struct fs_context *fc, > struct fs_parameter *param) > LSM_HOOK(int, 0, sb_alloc_security, struct super_block *sb) > +LSM_HOOK(void, LSM_RET_VOID, sb_delete, struct super_block *sb) > LSM_HOOK(void, LSM_RET_VOID, sb_free_security, struct super_block *sb) > LSM_HOOK(void, LSM_RET_VOID, sb_free_mnt_opts, void *mnt_opts) > LSM_HOOK(int, 0, sb_eat_lsm_opts, char *orig, void **mnt_opts) > diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h > index 970106d98306..e339b201f79b 100644 > --- a/include/linux/lsm_hooks.h > +++ b/include/linux/lsm_hooks.h > @@ -108,6 +108,8 @@ > * allocated. > * @sb contains the super_block structure to be modified. > * Return 0 if operation was successful. > + * @sb_delete: > + * Release objects tied to a superblock (e.g. inodes). It's customary here to add the line detailing the @sb argument. > * @sb_free_security: > * Deallocate and clear the sb->s_security field. > * @sb contains the super_block structure to be modified. > diff --git a/include/linux/security.h b/include/linux/security.h > index c35ea0ffccd9..c41a94e29b62 100644 > --- a/include/linux/security.h > +++ b/include/linux/security.h > @@ -288,6 +288,7 @@ void security_bprm_committed_creds(struct linux_binprm *bprm); > int security_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc); > int security_fs_context_parse_param(struct fs_context *fc, struct fs_parameter *param); > int security_sb_alloc(struct super_block *sb); > +void security_sb_delete(struct super_block *sb); > void security_sb_free(struct super_block *sb); > void security_free_mnt_opts(void **mnt_opts); > int security_sb_eat_lsm_opts(char *options, void **mnt_opts); > @@ -620,6 +621,9 @@ static inline int security_sb_alloc(struct super_block *sb) > return 0; > } > > +static inline void security_sb_delete(struct super_block *sb) > +{ } > + > static inline void security_sb_free(struct super_block *sb) > { } > > diff --git a/security/security.c b/security/security.c > index 9f979d4afe6c..1b4a73b2549a 100644 > --- a/security/security.c > +++ b/security/security.c > @@ -900,6 +900,11 @@ int security_sb_alloc(struct super_block *sb) > return rc; > } > > +void security_sb_delete(struct super_block *sb) > +{ > + call_void_hook(sb_delete, sb); > +} > + > void security_sb_free(struct super_block *sb) > { > call_void_hook(sb_free_security, sb); > -- > 2.30.0
