From 7b3552d3f9f6897851fc453b5131a967167e43c2 Mon Sep 17 00:00:00 2001
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Sat, 19 Mar 2022 13:38:25 +0530
Subject: [PATCH] bpf: Reject writes for PTR_TO_MAP_KEY in
check_helper_mem_access
It is not permitted to write to PTR_TO_MAP_KEY, but the current code in
check_helper_mem_access would allow for it, reject this case as well, as
helpers taking ARG_PTR_TO_UNINIT_MEM also take PTR_TO_MAP_KEY.
Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20220319080827.73251-4-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
kernel/bpf/verifier.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d953e62b5268d..9c1a02b82ecd0 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4861,6 +4861,11 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
return check_packet_access(env, regno, reg->off, access_size,
zero_size_allowed);
case PTR_TO_MAP_KEY:
+ if (meta && meta->raw_mode) {
+ verbose(env, "R%d cannot write into %s\n", regno,
+ reg_type_str(env, reg->type));
+ return -EACCES;
+ }
return check_mem_region_access(env, regno, reg->off, access_size,
reg->map_ptr->key_size, false);
case PTR_TO_MAP_VALUE: