From: Daniel Borkmann daniel@iogearbox.net
[ Upstream commit 3b4d9eb2ee74dd5ea7fa36cffb0ca7f5bc4924da ]
There is one more problematic case I noticed while recently fixing BPF kallsyms handling in cd7455f1013e ("bpf: Fix use after free in subprog's jited symbol removal") and that is bpf_get_prog_name().
If BTF has been attached to the prog, then we may be able to fetch the function signature type id in kallsyms through prog->aux->func_info[prog->aux->func_idx].type_id. However, while the BTF object itself is torn down via RCU callback, the prog's aux->func_info is immediately freed via kvfree(prog->aux->func_info) once the prog's refcount either hit zero or when subprograms were already exposed via kallsyms and we hit the error path added in 5482e9a93c83 ("bpf: Fix memleak in aux->func_info and aux->btf").
This violates RCU as well since kallsyms could be walked in parallel where we could access aux->func_info. Hence, defer kvfree() to after RCU grace period. Looking at ba64e7d85252 ("bpf: btf: support proper non-jit func info") there is no reason/dependency where we couldn't defer the kvfree(aux->func_info) into the RCU callback.
Fixes: 5482e9a93c83 ("bpf: Fix memleak in aux->func_info and aux->btf") Fixes: ba64e7d85252 ("bpf: btf: support proper non-jit func info") Signed-off-by: Daniel Borkmann daniel@iogearbox.net Signed-off-by: Alexei Starovoitov ast@kernel.org Acked-by: Yonghong Song yhs@fb.com Cc: Martin KaFai Lau kafai@fb.com Link: https://lore.kernel.org/bpf/875f2906a7c1a0691f2d567b4d8e4ea2739b1e88.1571779... Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/syscall.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index af5c60b07463e..aac966b32c42e 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1316,6 +1316,7 @@ static void __bpf_prog_put_rcu(struct rcu_head *rcu) { struct bpf_prog_aux *aux = container_of(rcu, struct bpf_prog_aux, rcu);
+ kvfree(aux->func_info); free_used_maps(aux); bpf_prog_uncharge_memlock(aux->prog); security_bpf_prog_free(aux); @@ -1326,7 +1327,6 @@ static void __bpf_prog_put_noref(struct bpf_prog *prog, bool deferred) { bpf_prog_kallsyms_del_all(prog); btf_put(prog->aux->btf); - kvfree(prog->aux->func_info); bpf_prog_free_linfo(prog);
if (deferred)