On Fri, Feb 05, 2021 at 03:57:37PM +0100, Mickaël Salaün wrote: > > On 05/02/2021 15:21, Serge E. Hallyn wrote: > > 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. > > What about "@sb contains the super_block structure being released."? That's good. Thanks. > > > >> * @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
