On Wed, 4 Oct 2023 at 21:38, Paul Moore <paul@xxxxxxxxxxxxxx> wrote: > > On Thu, Sep 28, 2023 at 9:04 AM Miklos Szeredi <mszeredi@xxxxxxxxxx> wrote: > > > > Add way to query the children of a particular mount. This is a more > > flexible way to iterate the mount tree than having to parse the complete > > /proc/self/mountinfo. > > > > Lookup the mount by 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. > > > > Return an array of new (64bit) mount ID's. Without privileges only mounts > > are listed which are reachable from the task's root. > > > > 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 | 69 ++++++++++++++++++++++++++ > > include/linux/syscalls.h | 3 ++ > > include/uapi/asm-generic/unistd.h | 5 +- > > include/uapi/linux/mount.h | 3 ++ > > 6 files changed, 81 insertions(+), 1 deletion(-) > > ... > > > diff --git a/fs/namespace.c b/fs/namespace.c > > index 3326ba2b2810..050e2d2af110 100644 > > --- a/fs/namespace.c > > +++ b/fs/namespace.c > > @@ -4970,6 +4970,75 @@ SYSCALL_DEFINE4(statmount, const struct __mount_arg __user *, req, > > return ret; > > } > > > > +static long do_listmount(struct vfsmount *mnt, u64 __user *buf, size_t bufsize, > > + const struct path *root, unsigned int flags) > > +{ > > + struct mount *r, *m = real_mount(mnt); > > + struct path rootmnt = { > > + .mnt = root->mnt, > > + .dentry = root->mnt->mnt_root > > + }; > > + long ctr = 0; > > + bool reachable_only = true; > > + int err; > > + > > + err = security_sb_statfs(mnt->mnt_root); > > + if (err) > > + return err; > > + > > + if (flags & LISTMOUNT_UNREACHABLE) { > > + if (!capable(CAP_SYS_ADMIN)) > > + return -EPERM; > > + reachable_only = false; > > + } > > + > > + if (reachable_only && !is_path_reachable(m, mnt->mnt_root, &rootmnt)) > > + return capable(CAP_SYS_ADMIN) ? 0 : -EPERM; > > + > > + list_for_each_entry(r, &m->mnt_mounts, mnt_child) { > > + if (reachable_only && > > + !is_path_reachable(r, r->mnt.mnt_root, root)) > > + continue; > > I believe we would want to move the security_sb_statfs() call from > above to down here; something like this I think ... > > err = security_sb_statfs(r->mnt.mnt_root); > if (err) > /* if we can't access the mount, pretend it doesn't exist */ > continue; Hmm. Why is this specific to listing mounts (i.e. why doesn't readdir have a similar filter)? Also why hasn't this come up with regards to the proc interfaces that list mounts? I just want to understand the big picture here. Thanks, Miklos