| Message ID | 20220603154028.24904-1-toke@redhat.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | [bpf,1/2] bpf: Fix calling global functions from BPF_PROG_TYPE_EXT programs | expand |
On Fri, Jun 03, 2022 at 09:10:26PM IST, Toke Høiland-Jørgensen wrote: > The verifier allows programs to call global functions as long as their > argument types match, using BTF to check the function arguments. One of the > allowed argument types to such global functions is PTR_TO_CTX; however the > check for this fails on BPF_PROG_TYPE_EXT functions because the verifier > uses the wrong type to fetch the vmlinux BTF ID for the program context > type. This failure is seen when an XDP program is loaded using > libxdp (which loads it as BPF_PROG_TYPE_EXT and attaches it to a global XDP > type program). > > Fix the issue by passing in the target program type instead of the > BPF_PROG_TYPE_EXT type to bpf_prog_get_ctx() when checking function > argument compatibility. > > The first Fixes tag refers to the latest commit that touched the code in > question, while the second one points to the code that first introduced > the global function call verification. > > Fixes: 3363bd0cfbb8 ("bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support") > Fixes: 51c39bb1d5d1 ("bpf: Introduce function-by-function verification") > Reported-by: Simon Sundberg <simon.sundberg@kau.se> > Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> > --- > kernel/bpf/btf.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c > index 7bccaa4646e5..361de7304c4d 100644 > --- a/kernel/bpf/btf.c > +++ b/kernel/bpf/btf.c > @@ -6054,6 +6054,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, > struct bpf_reg_state *regs, > bool ptr_to_mem_ok) > { > + enum bpf_prog_type prog_type = env->prog->type; > struct bpf_verifier_log *log = &env->log; > u32 i, nargs, ref_id, ref_obj_id = 0; > bool is_kfunc = btf_is_kernel(btf); > @@ -6095,6 +6096,9 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, > BTF_KFUNC_TYPE_KPTR_ACQUIRE, func_id); > } > > + if (prog_type == BPF_PROG_TYPE_EXT && env->prog->aux->dst_prog) > + prog_type = env->prog->aux->dst_prog->type; > + nit: it might be better to reuse resolve_prog_type here. > /* check that BTF function arguments match actual types that the > * verifier sees. > */ > @@ -6171,7 +6175,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, > return -EINVAL; > } > /* rest of the arguments can be anything, like normal kfunc */ > - } else if (btf_get_prog_ctx_type(log, btf, t, env->prog->type, i)) { > + } else if (btf_get_prog_ctx_type(log, btf, t, prog_type, i)) { > /* If function expects ctx type in BTF check that caller > * is passing PTR_TO_CTX. > */ > -- > 2.36.1 > -- Kartikeya
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 7bccaa4646e5..361de7304c4d 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6054,6 +6054,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, struct bpf_reg_state *regs, bool ptr_to_mem_ok) { + enum bpf_prog_type prog_type = env->prog->type; struct bpf_verifier_log *log = &env->log; u32 i, nargs, ref_id, ref_obj_id = 0; bool is_kfunc = btf_is_kernel(btf); @@ -6095,6 +6096,9 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, BTF_KFUNC_TYPE_KPTR_ACQUIRE, func_id); } + if (prog_type == BPF_PROG_TYPE_EXT && env->prog->aux->dst_prog) + prog_type = env->prog->aux->dst_prog->type; + /* check that BTF function arguments match actual types that the * verifier sees. */ @@ -6171,7 +6175,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, return -EINVAL; } /* rest of the arguments can be anything, like normal kfunc */ - } else if (btf_get_prog_ctx_type(log, btf, t, env->prog->type, i)) { + } else if (btf_get_prog_ctx_type(log, btf, t, prog_type, i)) { /* If function expects ctx type in BTF check that caller * is passing PTR_TO_CTX. */
The verifier allows programs to call global functions as long as their argument types match, using BTF to check the function arguments. One of the allowed argument types to such global functions is PTR_TO_CTX; however the check for this fails on BPF_PROG_TYPE_EXT functions because the verifier uses the wrong type to fetch the vmlinux BTF ID for the program context type. This failure is seen when an XDP program is loaded using libxdp (which loads it as BPF_PROG_TYPE_EXT and attaches it to a global XDP type program). Fix the issue by passing in the target program type instead of the BPF_PROG_TYPE_EXT type to bpf_prog_get_ctx() when checking function argument compatibility. The first Fixes tag refers to the latest commit that touched the code in question, while the second one points to the code that first introduced the global function call verification. Fixes: 3363bd0cfbb8 ("bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support") Fixes: 51c39bb1d5d1 ("bpf: Introduce function-by-function verification") Reported-by: Simon Sundberg <simon.sundberg@kau.se> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> --- kernel/bpf/btf.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)