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bpf: Reject writes for PTR_TO_MAP_KEY in check_helper_mem_access

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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: 69c087ba62 ("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>
This commit is contained in:
Kumar Kartikeya Dwivedi 2022-03-19 13:38:25 +05:30 committed by Alexei Starovoitov
parent 97e6d7dab1
commit 7b3552d3f9
1 changed files with 5 additions and 0 deletions
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5
kernel/bpf/verifier.c
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@ -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: