On Tue, Mar 28, 2017 at 4:46 PM, Mickaël Salaün <mic@xxxxxxxxxxx> wrote: > The goal of the program subtype is to be able to have different static > fine-grained verifications for a unique program type. > > The struct bpf_verifier_ops gets a new optional function: > is_valid_subtype(). This new verifier is called at the beginning of the > eBPF program verification to check if the (optional) program subtype is > valid. > > For now, only Landlock eBPF programs are using a program subtype (see > next commit) but this could be used by other program types in the future. > > Changes since v5: > * use a prog_subtype pointer and make it future-proof > * add subtype test > * constify bpf_load_program()'s subtype argument > * cleanup subtype initialization > * rebase > > Changes since v4: > * replace the "status" field with "version" (more generic) > * replace the "access" field with "ability" (less confusing) > > Changes since v3: > * remove the "origin" field > * add an "option" field > * cleanup comments > > Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx> > Cc: Alexei Starovoitov <ast@xxxxxxxxxx> > Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> > Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx> > Cc: David S. Miller <davem@xxxxxxxxxxxxx> > Link: https://lkml.kernel.org/r/20160827205559.GA43880@xxxxxxxxxxxxxxxxxxxxxxx > --- > [...] > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index c35ebfe6d84d..3d07b10ade5e 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -843,6 +879,26 @@ static int bpf_prog_load(union bpf_attr *attr) > if (err < 0) > goto free_prog; > > + /* copy eBPF program subtype from user space */ > + if (attr->prog_subtype) { > + __u32 size; > + > + size = check_user_buf((void __user *)attr->prog_subtype, > + attr->prog_subtype_size, > + sizeof(prog->subtype)); > + if (size < 0) { > + err = size; > + goto free_prog; > + } > + /* prog->subtype is __GFP_ZERO */ > + if (copy_from_user(&prog->subtype, > + u64_to_user_ptr(attr->prog_subtype), size) > + != 0) It might be worth adding a comment here about how the ToCToU of the check-then-copy doesn't matter in this case, since it's just a future-proofing of bits, etc. -Kees -- Kees Cook Pixel Security -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
