On Fri, Feb 11, 2022 at 8:43 PM Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
>
> On 2/11/22 1:11 PM, Yafang Shao wrote:
> > A new member pin_name is added into struct bpf_prog_aux, which will be
> > set when the prog is set and cleared when the pinned file is removed.
> >
> > Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> > ---
> > include/linux/bpf.h | 2 ++
> > include/uapi/linux/bpf.h | 1 +
> > kernel/bpf/inode.c | 20 +++++++++++++++++++-
> > 3 files changed, 22 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index 0ceb25b..9cf8055 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -933,6 +933,8 @@ struct bpf_prog_aux {
> > struct work_struct work;
> > struct rcu_head rcu;
> > };
> > +
> > + char pin_name[BPF_PIN_NAME_LEN];
> > };
>
> I'm afraid this is not possible. You are assuming a 1:1 relationship between prog
> and pin location, but it's really a 1:n (prog can be pinned in multiple locations
> and also across multiple mount instances).
Thanks for the explanation!
I didn't notice the 1:n relationship before. I will read the code more
to try to find if there's a good way to implement it.
> Also, you can create hard links of pins
> which are not handled via bpf_obj_do_pin().
>
Yes, it seems we should introduce bpf_{link, unlink, rename} first
instead of the simple_* one.
> > struct bpf_array_aux {
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index c14fed8..bada5cc 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -1217,6 +1217,7 @@ struct bpf_stack_build_id {
> > };
> >
> > #define BPF_OBJ_NAME_LEN 16U
> > +#define BPF_PIN_NAME_LEN 64U
> >
> > union bpf_attr {
> > struct { /* anonymous struct used by BPF_MAP_CREATE command */
> > diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
> > index 4477ca8..f1a8811 100644
> > --- a/kernel/bpf/inode.c
> > +++ b/kernel/bpf/inode.c
> > @@ -437,6 +437,8 @@ static int bpf_iter_link_pin_kernel(struct dentry *parent,
> > static int bpf_obj_do_pin(const char __user *pathname, void *raw,
> > enum bpf_type type)
> > {
> > + struct bpf_prog_aux *aux;
> > + struct bpf_prog *prog;
> > struct dentry *dentry;
> > struct inode *dir;
> > struct path path;
> > @@ -461,6 +463,10 @@ static int bpf_obj_do_pin(const char __user *pathname, void *raw,
> >
> > switch (type) {
> > case BPF_TYPE_PROG:
> > + prog = raw;
> > + aux = prog->aux;
> > + (void) strncpy_from_user(aux->pin_name, pathname, BPF_PIN_NAME_LEN);
> > + aux->pin_name[BPF_PIN_NAME_LEN - 1] = '\0';
> > ret = vfs_mkobj(dentry, mode, bpf_mkprog, raw);
> > break;
> > case BPF_TYPE_MAP:
> > @@ -611,12 +617,24 @@ static int bpf_show_options(struct seq_file *m, struct dentry *root)
> >
> > static void bpf_free_inode(struct inode *inode)
> > {
> > + struct bpf_prog_aux *aux;
> > + struct bpf_prog *prog;
> > enum bpf_type type;
> >
> > if (S_ISLNK(inode->i_mode))
> > kfree(inode->i_link);
> > - if (!bpf_inode_type(inode, &type))
> > + if (!bpf_inode_type(inode, &type)) {
> > + switch (type) {
> > + case BPF_TYPE_PROG:
> > + prog = inode->i_private;
> > + aux = prog->aux;
> > + aux->pin_name[0] = '\0';
> > + break;
> > + default:
> > + break;
> > + }
> > bpf_any_put(inode->i_private, type);
> > + }
> > free_inode_nonrcu(inode);
> > }
> >
> >
>
--
Thanks
Yafang
