On Thu, Sep 28, 2023 at 9:03 AM Miklos Szeredi <mszeredi@xxxxxxxxxx> wrote: > > Add a way to query attributes of a single mount instead of having to parse > the complete /proc/$PID/mountinfo, which might be huge. > > Lookup the mount the new 64bit mount ID. If a mount needs to be queried > based on path, then statx(2) can be used to first query the mount ID > belonging to the path. > > Design is based on a suggestion by Linus: > > "So I'd suggest something that is very much like "statfsat()", which gets > a buffer and a length, and returns an extended "struct statfs" *AND* > just a string description at the end." > > The interface closely mimics that of statx. > > Handle ASCII attributes by appending after the end of the structure (as per > above suggestion). Pointers to strings are stored in u64 members to make > the structure the same regardless of pointer size. Strings are nul > terminated. > > Link: https://lore.kernel.org/all/CAHk-=wh5YifP7hzKSbwJj94+DZ2czjrZsczy6GBimiogZws=rg@xxxxxxxxxxxxxx/ > Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx> > --- > arch/x86/entry/syscalls/syscall_32.tbl | 1 + > arch/x86/entry/syscalls/syscall_64.tbl | 1 + > fs/namespace.c | 283 +++++++++++++++++++++++++ > fs/statfs.c | 1 + > include/linux/syscalls.h | 5 + > include/uapi/asm-generic/unistd.h | 5 +- > include/uapi/linux/mount.h | 56 +++++ > 7 files changed, 351 insertions(+), 1 deletion(-) ... > diff --git a/fs/namespace.c b/fs/namespace.c > index c3a41200fe70..3326ba2b2810 100644 > --- a/fs/namespace.c > +++ b/fs/namespace.c ... > +static int do_statmount(struct stmt_state *s) > +{ > + struct statmnt *sm = &s->sm; > + struct mount *m = real_mount(s->mnt); > + size_t copysize = min_t(size_t, s->bufsize, sizeof(*sm)); > + int err; > + > + err = security_sb_statfs(s->mnt->mnt_root); > + if (err) > + return err; Thank you for adding the security_sb_statfs() call to this operation, however I believe we want to place it *after* the capability check to be consistent with other LSM calls. > + if (!capable(CAP_SYS_ADMIN) && > + !is_path_reachable(m, m->mnt.mnt_root, &s->root)) > + return -EPERM; > + > + stmt_numeric(s, STMT_SB_BASIC, stmt_sb_basic); > + stmt_numeric(s, STMT_MNT_BASIC, stmt_mnt_basic); > + stmt_numeric(s, STMT_PROPAGATE_FROM, stmt_propagate_from); > + stmt_string(s, STMT_FS_TYPE, stmt_fs_type, &sm->fs_type); > + stmt_string(s, STMT_MNT_ROOT, stmt_mnt_root, &sm->mnt_root); > + stmt_string(s, STMT_MNT_POINT, stmt_mnt_point, &sm->mnt_point); > + > + if (s->err) > + return s->err; > + > + /* Return the number of bytes copied to the buffer */ > + sm->size = copysize + s->pos; > + > + if (copy_to_user(s->buf, sm, copysize)) > + return -EFAULT; > + > + return 0; > +} -- paul-moore.com
