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bpf: Fix a btf decl_tag bug when tagging a function
[ Upstream commitd7e7b42f4f
] syzbot reported a btf decl_tag bug with stack trace below: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] CPU: 0 PID: 3592 Comm: syz-executor914 Not tainted 5.16.0-syzkaller-11424-gb7892f7d5cb2 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:btf_type_vlen include/linux/btf.h:231 [inline] RIP: 0010:btf_decl_tag_resolve+0x83e/0xaa0 kernel/bpf/btf.c:3910 ... Call Trace: <TASK> btf_resolve+0x251/0x1020 kernel/bpf/btf.c:4198 btf_check_all_types kernel/bpf/btf.c:4239 [inline] btf_parse_type_sec kernel/bpf/btf.c:4280 [inline] btf_parse kernel/bpf/btf.c:4513 [inline] btf_new_fd+0x19fe/0x2370 kernel/bpf/btf.c:6047 bpf_btf_load kernel/bpf/syscall.c:4039 [inline] __sys_bpf+0x1cbb/0x5970 kernel/bpf/syscall.c:4679 __do_sys_bpf kernel/bpf/syscall.c:4738 [inline] __se_sys_bpf kernel/bpf/syscall.c:4736 [inline] __x64_sys_bpf+0x75/0xb0 kernel/bpf/syscall.c:4736 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae The kasan error is triggered with an illegal BTF like below: type 0: void type 1: int type 2: decl_tag to func type 3 type 3: func to func_proto type 8 The total number of types is 4 and the type 3 is illegal since its func_proto type is out of range. Currently, the target type of decl_tag can be struct/union, var or func. Both struct/union and var implemented their own 'resolve' callback functions and hence handled properly in kernel. But func type doesn't have 'resolve' callback function. When btf_decl_tag_resolve() tries to check func type, it tries to get vlen of its func_proto type, which triggered the above kasan error. To fix the issue, btf_decl_tag_resolve() needs to do btf_func_check() before trying to accessing func_proto type. In the current implementation, func type is checked with btf_func_check() in the main checking function btf_check_all_types(). To fix the above kasan issue, let us implement 'resolve' callback func type properly. The 'resolve' callback will be also called in btf_check_all_types() for func types. Fixes:b5ea834dde
("bpf: Support for new btf kind BTF_KIND_TAG") Reported-by: syzbot+53619be9444215e785ed@syzkaller.appspotmail.com Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Martin KaFai Lau <kafai@fb.com> Link: https://lore.kernel.org/bpf/20220203191727.741862-1-yhs@fb.com Signed-off-by: Sasha Levin <sashal@kernel.org>
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3e4015af1a
commit
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1 changed files with 21 additions and 8 deletions
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@ -403,6 +403,9 @@ static struct btf_type btf_void;
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static int btf_resolve(struct btf_verifier_env *env,
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static int btf_resolve(struct btf_verifier_env *env,
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const struct btf_type *t, u32 type_id);
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const struct btf_type *t, u32 type_id);
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static int btf_func_check(struct btf_verifier_env *env,
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const struct btf_type *t);
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static bool btf_type_is_modifier(const struct btf_type *t)
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static bool btf_type_is_modifier(const struct btf_type *t)
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{
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{
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/* Some of them is not strictly a C modifier
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/* Some of them is not strictly a C modifier
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@ -579,6 +582,7 @@ static bool btf_type_needs_resolve(const struct btf_type *t)
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btf_type_is_struct(t) ||
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btf_type_is_struct(t) ||
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btf_type_is_array(t) ||
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btf_type_is_array(t) ||
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btf_type_is_var(t) ||
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btf_type_is_var(t) ||
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btf_type_is_func(t) ||
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btf_type_is_decl_tag(t) ||
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btf_type_is_decl_tag(t) ||
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btf_type_is_datasec(t);
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btf_type_is_datasec(t);
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}
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}
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@ -3533,9 +3537,24 @@ static s32 btf_func_check_meta(struct btf_verifier_env *env,
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return 0;
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return 0;
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}
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}
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static int btf_func_resolve(struct btf_verifier_env *env,
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const struct resolve_vertex *v)
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{
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const struct btf_type *t = v->t;
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u32 next_type_id = t->type;
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int err;
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err = btf_func_check(env, t);
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if (err)
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return err;
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env_stack_pop_resolved(env, next_type_id, 0);
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return 0;
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}
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static struct btf_kind_operations func_ops = {
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static struct btf_kind_operations func_ops = {
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.check_meta = btf_func_check_meta,
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.check_meta = btf_func_check_meta,
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.resolve = btf_df_resolve,
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.resolve = btf_func_resolve,
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.check_member = btf_df_check_member,
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.check_member = btf_df_check_member,
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.check_kflag_member = btf_df_check_kflag_member,
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.check_kflag_member = btf_df_check_kflag_member,
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.log_details = btf_ref_type_log,
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.log_details = btf_ref_type_log,
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@ -4156,7 +4175,7 @@ static bool btf_resolve_valid(struct btf_verifier_env *env,
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return !btf_resolved_type_id(btf, type_id) &&
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return !btf_resolved_type_id(btf, type_id) &&
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!btf_resolved_type_size(btf, type_id);
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!btf_resolved_type_size(btf, type_id);
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if (btf_type_is_decl_tag(t))
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if (btf_type_is_decl_tag(t) || btf_type_is_func(t))
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return btf_resolved_type_id(btf, type_id) &&
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return btf_resolved_type_id(btf, type_id) &&
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!btf_resolved_type_size(btf, type_id);
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!btf_resolved_type_size(btf, type_id);
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@ -4246,12 +4265,6 @@ static int btf_check_all_types(struct btf_verifier_env *env)
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if (err)
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if (err)
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return err;
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return err;
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}
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}
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if (btf_type_is_func(t)) {
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err = btf_func_check(env, t);
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if (err)
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return err;
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}
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}
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}
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return 0;
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return 0;
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