Re: [PATCH stable 6.6 05/10] bpf: check changes_pkt_data property for extension programs

[Sasha Levin <sashal@kernel.org>]

[ Sasha's backport helper bot ]

Hi,

Summary of potential issues:
ℹ️ This is part 05/10 of a series
⚠️ Found follow-up fixes in mainline

The upstream commit SHA1 provided is correct: 81f6d0530ba031b5f038a091619bf2ff29568852

WARNING: Author mismatch between patch and upstream commit:
Backport author: Shung-Hsi Yu<shung-hsi.yu@suse.com>
Commit author: Eduard Zingerman<eddyz87@gmail.com>

Status in newer kernel trees:
6.14.y | Present (exact SHA1)
6.12.y | Present (different SHA1: 3846e2bea565)

Found fixes commits:
ac6542ad9275 bpf: fix null dereference when computing changes_pkt_data of prog w/o subprogs

Note: The patch differs from the upstream commit:
---
1:  81f6d0530ba03 ! 1:  9b08cd4de7325 bpf: check changes_pkt_data property for extension programs
    @@ Metadata
      ## Commit message ##
         bpf: check changes_pkt_data property for extension programs
     
    +    commit 81f6d0530ba031b5f038a091619bf2ff29568852 upstream.
    +
         When processing calls to global sub-programs, verifier decides whether
         to invalidate all packet pointers in current state depending on the
         changes_pkt_data property of the global sub-program.
    @@ Commit message
         Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
         Link: https://lore.kernel.org/r/20241210041100.1898468-6-eddyz87@gmail.com
         Signed-off-by: Alexei Starovoitov <ast@kernel.org>
    +    [ shung-hsi.yu: adapt to missing fields in "struct bpf_prog_aux". Context
    +    difference in jit_subprogs() because BPF Exception is not supported. Context
    +    difference in bpf_check() because commit 5b5f51bff1b6 "bpf:
    +    no_caller_saved_registers attribute for helper calls" is not present. ]
    +    Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
     
      ## include/linux/bpf.h ##
     @@ include/linux/bpf.h: struct bpf_prog_aux {
    - 	bool is_extended; /* true if extended by freplace program */
    - 	bool jits_use_priv_stack;
    - 	bool priv_stack_requested;
    + 	bool sleepable;
    + 	bool tail_call_reachable;
    + 	bool xdp_has_frags;
     +	bool changes_pkt_data;
    - 	u64 prog_array_member_cnt; /* counts how many times as member of prog_array */
    - 	struct mutex ext_mutex; /* mutex for is_extended and prog_array_member_cnt */
    - 	struct bpf_arena *arena;
    + 	/* BTF_KIND_FUNC_PROTO for valid attach_btf_id */
    + 	const struct btf_type *attach_func_proto;
    + 	/* function name for valid attach_btf_id */
     
      ## kernel/bpf/verifier.c ##
     @@ kernel/bpf/verifier.c: static int check_cfg(struct bpf_verifier_env *env)
    @@ kernel/bpf/verifier.c: static int check_cfg(struct bpf_verifier_env *env)
      err_free:
      	kvfree(insn_state);
     @@ kernel/bpf/verifier.c: static int jit_subprogs(struct bpf_verifier_env *env)
    + 		}
      		func[i]->aux->num_exentries = num_exentries;
      		func[i]->aux->tail_call_reachable = env->subprog_info[i].tail_call_reachable;
    - 		func[i]->aux->exception_cb = env->subprog_info[i].is_exception_cb;
     +		func[i]->aux->changes_pkt_data = env->subprog_info[i].changes_pkt_data;
    - 		if (!i)
    - 			func[i]->aux->exception_boundary = env->seen_exception;
      		func[i] = bpf_int_jit_compile(func[i]);
    + 		if (!func[i]->jited) {
    + 			err = -ENOTSUPP;
     @@ kernel/bpf/verifier.c: int bpf_check_attach_target(struct bpf_verifier_log *log,
      					"Extension programs should be JITed\n");
      				return -EINVAL;
    @@ kernel/bpf/verifier.c: int bpf_check(struct bpf_prog **prog, union bpf_attr *att
     +	if (ret)
     +		goto skip_full_check;
     +
    - 	ret = mark_fastcall_patterns(env);
    - 	if (ret < 0)
    - 		goto skip_full_check;
    + 	ret = do_check_subprogs(env);
    + 	ret = ret ?: do_check_main(env);
    + 
---

NOTE: These results are for this patch alone. Full series testing will be
performed when all parts are received.

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.12.y       |  Success    |  Success   |