commit f858c2b2ca04fc7ead291821a793638ae120c11d upstream
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.
v2: - Use resolve_prog_type()
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 Link: https://lore.kernel.org/r/20220606075253.28422-1-toke@redhat.com Signed-off-by: Alexei Starovoitov ast@kernel.org [ backport: open-code missing resolve_prog_type() helper, resolve context diff ] Signed-off-by: Toke Høiland-Jørgensen toke@redhat.com --- kernel/bpf/btf.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 40df35088cdb..3cfba41a0829 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -5441,6 +5441,8 @@ 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 == BPF_PROG_TYPE_EXT ? + env->prog->aux->dst_prog->type : env->prog->type; struct bpf_verifier_log *log = &env->log; const char *func_name, *ref_tname; const struct btf_type *t, *ref_t; @@ -5533,8 +5535,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, reg_ref_tname); return -EINVAL; } - } 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. */