From: Daniel Borkmann <daniel@iogearbox.net>
Date: Tue, 22 Oct 2019 23:30:38 +0200
Subject: bpf: Fix use after free in bpf_get_prog_name
Patch-mainline: v5.4-rc6
Git-commit: 3b4d9eb2ee74dd5ea7fa36cffb0ca7f5bc4924da
References: bsc#1155518 bnc#1151927 5.3.11
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/875f2906a7c1a0691f2d567b4d8e4ea2739b1e88.1571779205.git.daniel@iogearbox.net
Acked-by: Gary Lin <glin@suse.com>
---
kernel/bpf/syscall.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1326,6 +1326,7 @@ static void __bpf_prog_put_rcu(struct rc
{
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);
@@ -1336,7 +1337,6 @@ static void __bpf_prog_put_noref(struct
{
bpf_prog_kallsyms_del_all(prog);
btf_put(prog->aux->btf);
- kvfree(prog->aux->func_info);
bpf_prog_free_linfo(prog);
if (deferred)