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bpf: Relax KF_ACQUIRE kfuncs strict type matching constraint

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Currently we cannot pass zero offset (implicit cast) or non-zero offset
pointers to KF_ACQUIRE kfuncs. This is because KF_ACQUIRE kfuncs
requires strict type matching, but zero offset or non-zero offset does
not change the type of pointer, which causes the ebpf program to be
rejected by the verifier.

This can cause some problems, one example is that bpf_skb_peek_tail
kfunc [0] cannot be implemented by just passing in non-zero offset
pointers. We cannot pass pointers like &sk->sk_write_queue (non-zero
offset) or &sk->__sk_common (zero offset) to KF_ACQUIRE kfuncs.

This patch makes KF_ACQUIRE kfuncs not require strict type matching.

[0]: https://lore.kernel.org/bpf/AM6PR03MB5848CA39CB4B7A4397D380B099B12@AM6PR03MB5848.eurprd03.prod.outlook.com/

Signed-off-by: Juntong Deng <juntong.deng@outlook.com>
Link: https://lore.kernel.org/r/AM6PR03MB5848FD2BD89BF0B6B5AA3B4C99952@AM6PR03MB5848.eurprd03.prod.outlook.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Juntong Deng 2024-08-28 20:48:11 +01:00 committed by Alexei Starovoitov
parent c264487e54
commit f633919d13
1 changed files with 1 additions and 2 deletions
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3
kernel/bpf/verifier.c
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@ -11513,8 +11513,7 @@ static int process_kf_arg_ptr_to_btf_id(struct bpf_verifier_env *env,
* btf_struct_ids_match() to walk the struct at the 0th offset, and
* resolve types.
*/
if (is_kfunc_acquire(meta) ||
(is_kfunc_release(meta) && reg->ref_obj_id) ||
if ((is_kfunc_release(meta) && reg->ref_obj_id) ||
btf_type_ids_nocast_alias(&env->log, reg_btf, reg_ref_id, meta->btf, ref_id))
strict_type_match = true;