linux-stable.git/kernel/bpf/btf.c, branch v6.1.78

bpf: Fix an error in verifying a field in a union

2023-09-13T07:42:30+00:00

[ Upstream commit 33937607efa050d9e237e0c4ac4ada02d961c466 ]

We are utilizing BPF LSM to monitor BPF operations within our container
environment. When we add support for raw_tracepoint, it hits below
error.

; (const void *)attr->raw_tracepoint.name);
27: (79) r3 = *(u64 *)(r2 +0)
access beyond the end of member map_type (mend:4) in struct (anon) with off 0 size 8

It can be reproduced with below BPF prog.

SEC("lsm/bpf")
int BPF_PROG(bpf_audit, int cmd, union bpf_attr *attr, unsigned int size)
{
	switch (cmd) {
	case BPF_RAW_TRACEPOINT_OPEN:
		bpf_printk("raw_tracepoint is %s", attr->raw_tracepoint.name);
		break;
	default:
		break;
	}
	return 0;
}

The reason is that when accessing a field in a union, such as bpf_attr,
if the field is located within a nested struct that is not the first
member of the union, it can result in incorrect field verification.

  union bpf_attr {
      struct {
          __u32 map_type; <<<< Actually it will find that field.
          __u32 key_size;
          __u32 value_size;
         ...
      };
      ...
      struct {
          __u64 name;    <<<< We want to verify this field.
          __u32 prog_fd;
      } raw_tracepoint;
  };

Considering the potential deep nesting levels, finding a perfect
solution to address this issue has proven challenging. Therefore, I
propose a solution where we simply skip the verification process if the
field in question is located within a union.

Fixes: 7e3617a72df3 ("bpf: Add array support to btf_struct_access")
Signed-off-by: Yafang Shao 
Link: https://lore.kernel.org/r/20230713025642.27477-4-laoar.shao@gmail.com
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Sasha Levin

bpf, btf: Warn but return no error for NULL btf from __register_btf_kfunc_id_set()

2023-07-19T14:22:05+00:00

[ Upstream commit 3de4d22cc9ac7c9f38e10edcf54f9a8891a9c2aa ]

__register_btf_kfunc_id_set() assumes .BTF to be part of the module's .ko
file if CONFIG_DEBUG_INFO_BTF is enabled. If that's not the case, the
function prints an error message and return an error. As a result, such
modules cannot be loaded.

However, the section could be stripped out during a build process. It would
be better to let the modules loaded, because their basic functionalities
have no problem [0], though the BTF functionalities will not be supported.
Make the function to lower the level of the message from error to warn, and
return no error.

  [0] https://lore.kernel.org/bpf/20220219082037.ow2kbq5brktf4f2u@apollo.legion

Fixes: c446fdacb10d ("bpf: fix register_btf_kfunc_id_set for !CONFIG_DEBUG_INFO_BTF")
Reported-by: Alexander Egorenkov 
Suggested-by: Kumar Kartikeya Dwivedi 
Signed-off-by: SeongJae Park 
Signed-off-by: Daniel Borkmann 
Acked-by: Jiri Olsa 
Link: https://lore.kernel.org/bpf/87y228q66f.fsf@oc8242746057.ibm.com
Link: https://lore.kernel.org/bpf/20220219082037.ow2kbq5brktf4f2u@apollo.legion
Link: https://lore.kernel.org/bpf/20230701171447.56464-1-sj@kernel.org
Signed-off-by: Sasha Levin

bpf/btf: Accept function names that contain dots

2023-06-28T09:12:33+00:00

[ Upstream commit 9724160b3942b0a967b91a59f81da5593f28b8ba ]

When building a kernel with LLVM=1, LLVM_IAS=0 and CONFIG_KASAN=y, LLVM
leaves DWARF tags for the "asan.module_ctor" & co symbols. In turn,
pahole creates BTF_KIND_FUNC entries for these and this makes the BTF
metadata validation fail because they contain a dot.

In a dramatic turn of event, this BTF verification failure can cause
the netfilter_bpf initialization to fail, causing netfilter_core to
free the netfilter_helper hashmap and netfilter_ftp to trigger a
use-after-free. The risk of u-a-f in netfilter will be addressed
separately but the existence of "asan.module_ctor" debug info under some
build conditions sounds like a good enough reason to accept functions
that contain dots in BTF.

Although using only LLVM=1 is the recommended way to compile clang-based
kernels, users can certainly do LLVM=1, LLVM_IAS=0 as well and we still
try to support that combination according to Nick. To clarify:

  - > v5.10 kernel, LLVM=1 (LLVM_IAS=0 is not the default) is recommended,
    but user can still have LLVM=1, LLVM_IAS=0 to trigger the issue

  - <= 5.10 kernel, LLVM=1 (LLVM_IAS=0 is the default) is recommended in
    which case GNU as will be used

Fixes: 1dc92851849c ("bpf: kernel side support for BTF Var and DataSec")
Signed-off-by: Florent Revest 
Signed-off-by: Daniel Borkmann 
Acked-by: Andrii Nakryiko 
Cc: Yonghong Song 
Cc: Nick Desaulniers 
Link: https://lore.kernel.org/bpf/20230615145607.3469985-1-revest@chromium.org
Signed-off-by: Sasha Levin

bpf: Fix race between btf_put and btf_idr walk.

2023-05-11T14:03:26+00:00

[ Upstream commit acf1c3d68e9a31f10d92bc67ad4673cdae5e8d92 ]

Florian and Eduard reported hard dead lock:
[   58.433327]  _raw_spin_lock_irqsave+0x40/0x50
[   58.433334]  btf_put+0x43/0x90
[   58.433338]  bpf_find_btf_id+0x157/0x240
[   58.433353]  btf_parse_fields+0x921/0x11c0

This happens since btf->refcount can be 1 at the time of btf_put() and
btf_put() will call btf_free_id() which will try to grab btf_idr_lock
and will dead lock.
Avoid the issue by doing btf_put() without locking.

Fixes: 3d78417b60fb ("bpf: Add bpf_btf_find_by_name_kind() helper.")
Fixes: 1e89106da253 ("bpf: Add bpf_core_add_cands() and wire it into bpf_core_apply_relo_insn().")
Reported-by: Florian Westphal 
Reported-by: Eduard Zingerman 
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Daniel Borkmann 
Tested-by: Eduard Zingerman 
Link: https://lore.kernel.org/bpf/20230421014901.70908-1-alexei.starovoitov@gmail.com
Signed-off-by: Sasha Levin

bpf/btf: Fix is_int_ptr()

2023-05-11T14:03:21+00:00

[ Upstream commit 91f2dc6838c19342f7f2993627c622835cc24890 ]

When tracing a kernel function with arg type is u32*, btf_ctx_access()
would report error: arg2 type INT is not a struct.

The commit bb6728d75611 ("bpf: Allow access to int pointer arguments
in tracing programs") added support for int pointer, but did not skip
modifiers before checking it's type. This patch fixes it.

Fixes: bb6728d75611 ("bpf: Allow access to int pointer arguments in tracing programs")
Co-developed-by: Chengming Zhou 
Signed-off-by: Chengming Zhou 
Signed-off-by: Feng Zhou 
Signed-off-by: Daniel Borkmann 
Acked-by: Jiri Olsa 
Link: https://lore.kernel.org/bpf/20230410085908.98493-2-zhoufeng.zf@bytedance.com
Signed-off-by: Sasha Levin

btf: fix resolving BTF_KIND_VAR after ARRAY, STRUCT, UNION, PTR

2023-03-17T07:50:26+00:00

[ Upstream commit 9b459804ff9973e173fabafba2a1319f771e85fa ]

btf_datasec_resolve contains a bug that causes the following BTF
to fail loading:

    [1] DATASEC a size=2 vlen=2
        type_id=4 offset=0 size=1
        type_id=7 offset=1 size=1
    [2] INT (anon) size=1 bits_offset=0 nr_bits=8 encoding=(none)
    [3] PTR (anon) type_id=2
    [4] VAR a type_id=3 linkage=0
    [5] INT (anon) size=1 bits_offset=0 nr_bits=8 encoding=(none)
    [6] TYPEDEF td type_id=5
    [7] VAR b type_id=6 linkage=0

This error message is printed during btf_check_all_types:

    [1] DATASEC a size=2 vlen=2
        type_id=7 offset=1 size=1 Invalid type

By tracing btf_*_resolve we can pinpoint the problem:

    btf_datasec_resolve(depth: 1, type_id: 1, mode: RESOLVE_TBD) = 0
        btf_var_resolve(depth: 2, type_id: 4, mode: RESOLVE_TBD) = 0
            btf_ptr_resolve(depth: 3, type_id: 3, mode: RESOLVE_PTR) = 0
        btf_var_resolve(depth: 2, type_id: 4, mode: RESOLVE_PTR) = 0
    btf_datasec_resolve(depth: 1, type_id: 1, mode: RESOLVE_PTR) = -22

The last invocation of btf_datasec_resolve should invoke btf_var_resolve
by means of env_stack_push, instead it returns EINVAL. The reason is that
env_stack_push is never executed for the second VAR.

    if (!env_type_is_resolve_sink(env, var_type) &&
        !env_type_is_resolved(env, var_type_id)) {
        env_stack_set_next_member(env, i + 1);
        return env_stack_push(env, var_type, var_type_id);
    }

env_type_is_resolve_sink() changes its behaviour based on resolve_mode.
For RESOLVE_PTR, we can simplify the if condition to the following:

    (btf_type_is_modifier() || btf_type_is_ptr) && !env_type_is_resolved()

Since we're dealing with a VAR the clause evaluates to false. This is
not sufficient to trigger the bug however. The log output and EINVAL
are only generated if btf_type_id_size() fails.

    if (!btf_type_id_size(btf, &type_id, &type_size)) {
        btf_verifier_log_vsi(env, v->t, vsi, "Invalid type");
        return -EINVAL;
    }

Most types are sized, so for example a VAR referring to an INT is not a
problem. The bug is only triggered if a VAR points at a modifier. Since
we skipped btf_var_resolve that modifier was also never resolved, which
means that btf_resolved_type_id returns 0 aka VOID for the modifier.
This in turn causes btf_type_id_size to return NULL, triggering EINVAL.

To summarise, the following conditions are necessary:

- VAR pointing at PTR, STRUCT, UNION or ARRAY
- Followed by a VAR pointing at TYPEDEF, VOLATILE, CONST, RESTRICT or
  TYPE_TAG

The fix is to reset resolve_mode to RESOLVE_TBD before attempting to
resolve a VAR from a DATASEC.

Fixes: 1dc92851849c ("bpf: kernel side support for BTF Var and DataSec")
Signed-off-by: Lorenz Bauer 
Link: https://lore.kernel.org/r/20230306112138.155352-2-lmb@isovalent.com
Signed-off-by: Martin KaFai Lau 
Signed-off-by: Sasha Levin

bpf: Fix global subprog context argument resolution logic

2023-03-10T08:33:06+00:00

[ Upstream commit d384dce281ed1b504fae2e279507827638d56fa3 ]

KPROBE program's user-facing context type is defined as typedef
bpf_user_pt_regs_t. This leads to a problem when trying to passing
kprobe/uprobe/usdt context argument into global subprog, as kernel
always strip away mods and typedefs of user-supplied type, but takes
expected type from bpf_ctx_convert as is, which causes mismatch.

Current way to work around this is to define a fake struct with the same
name as expected typedef:

  struct bpf_user_pt_regs_t {};

  __noinline my_global_subprog(struct bpf_user_pt_regs_t *ctx) { ... }

This patch fixes the issue by resolving expected type, if it's not
a struct. It still leaves the above work-around working for backwards
compatibility.

Fixes: 91cc1a99740e ("bpf: Annotate context types")
Signed-off-by: Andrii Nakryiko 
Signed-off-by: Daniel Borkmann 
Acked-by: Stanislav Fomichev 
Link: https://lore.kernel.org/bpf/20230216045954.3002473-2-andrii@kernel.org
Signed-off-by: Sasha Levin

bpf: Add missing btf_put to register_btf_id_dtor_kfuncs

2023-02-09T10:28:01+00:00

[ Upstream commit 74bc3a5acc82f020d2e126f56c535d02d1e74e37 ]

We take the BTF reference before we register dtors and we need
to put it back when it's done.

We probably won't se a problem with kernel BTF, but module BTF
would stay loaded (because of the extra ref) even when its module
is removed.

Cc: Kumar Kartikeya Dwivedi 
Fixes: 5ce937d613a4 ("bpf: Populate pairs of btf_id and destructor kfunc in btf")
Acked-by: Kumar Kartikeya Dwivedi 
Signed-off-by: Jiri Olsa 
Link: https://lore.kernel.org/r/20230120122148.1522359-1-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Sasha Levin

bpf: Prevent decl_tag from being referenced in func_proto arg

2022-12-31T12:33:03+00:00

[ Upstream commit f17472d4599697d701aa239b4c475a506bccfd19 ]

Syzkaller managed to hit another decl_tag issue:

  btf_func_proto_check kernel/bpf/btf.c:4506 [inline]
  btf_check_all_types kernel/bpf/btf.c:4734 [inline]
  btf_parse_type_sec+0x1175/0x1980 kernel/bpf/btf.c:4763
  btf_parse kernel/bpf/btf.c:5042 [inline]
  btf_new_fd+0x65a/0xb00 kernel/bpf/btf.c:6709
  bpf_btf_load+0x6f/0x90 kernel/bpf/syscall.c:4342
  __sys_bpf+0x50a/0x6c0 kernel/bpf/syscall.c:5034
  __do_sys_bpf kernel/bpf/syscall.c:5093 [inline]
  __se_sys_bpf kernel/bpf/syscall.c:5091 [inline]
  __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5091
  do_syscall_64+0x54/0x70 arch/x86/entry/common.c:48

This seems similar to commit ea68376c8bed ("bpf: prevent decl_tag from being
referenced in func_proto") but for the argument.

Reported-by: syzbot+8dd0551dda6020944c5d@syzkaller.appspotmail.com
Signed-off-by: Stanislav Fomichev 
Signed-off-by: Daniel Borkmann 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/bpf/20221123035422.872531-2-sdf@google.com
Signed-off-by: Sasha Levin

bpf: prevent decl_tag from being referenced in func_proto

2022-10-17T17:56:12+00:00

Syzkaller was able to hit the following issue:

------------[ cut here ]------------
WARNING: CPU: 0 PID: 3609 at kernel/bpf/btf.c:1946
btf_type_id_size+0x2d5/0x9d0 kernel/bpf/btf.c:1946
Modules linked in:
CPU: 0 PID: 3609 Comm: syz-executor361 Not tainted
6.0.0-syzkaller-02734-g0326074ff465 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 09/22/2022
RIP: 0010:btf_type_id_size+0x2d5/0x9d0 kernel/bpf/btf.c:1946
Code: ef e8 7f 8e e4 ff 41 83 ff 0b 77 28 f6 44 24 10 18 75 3f e8 6d 91
e4 ff 44 89 fe bf 0e 00 00 00 e8 20 8e e4 ff e8 5b 91 e4 ff <0f> 0b 45
31 f6 e9 98 02 00 00 41 83 ff 12 74 18 e8 46 91 e4 ff 44
RSP: 0018:ffffc90003cefb40 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000002 RCX: 0000000000000000
RDX: ffff8880259c0000 RSI: ffffffff81968415 RDI: 0000000000000005
RBP: ffff88801270ca00 R08: 0000000000000005 R09: 000000000000000e
R10: 0000000000000011 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000011 R14: ffff888026ee6424 R15: 0000000000000011
FS:  000055555641b300(0000) GS:ffff8880b9a00000(0000)
knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000f2e258 CR3: 000000007110e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 
 btf_func_proto_check kernel/bpf/btf.c:4447 [inline]
 btf_check_all_types kernel/bpf/btf.c:4723 [inline]
 btf_parse_type_sec kernel/bpf/btf.c:4752 [inline]
 btf_parse kernel/bpf/btf.c:5026 [inline]
 btf_new_fd+0x1926/0x1e70 kernel/bpf/btf.c:6892
 bpf_btf_load kernel/bpf/syscall.c:4324 [inline]
 __sys_bpf+0xb7d/0x4cf0 kernel/bpf/syscall.c:5010
 __do_sys_bpf kernel/bpf/syscall.c:5069 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5067 [inline]
 __x64_sys_bpf+0x75/0xb0 kernel/bpf/syscall.c:5067
 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+0x63/0xcd
RIP: 0033:0x7f0fbae41c69
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89
f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01
f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc8aeb6228 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f0fbae41c69
RDX: 0000000000000020 RSI: 0000000020000140 RDI: 0000000000000012
RBP: 00007f0fbae05e10 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000246 R12: 00007f0fbae05ea0
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 

Looks like it tries to create a func_proto which return type is
decl_tag. For the details, see Martin's spot on analysis in [0].

0: https://lore.kernel.org/bpf/CAKH8qBuQDLva_hHxxBuZzyAcYNO4ejhovz6TQeVSk8HY-2SO6g@mail.gmail.com/T/#mea6524b3fcd6298347432226e81b1e6155efc62c

Cc: Yonghong Song 
Cc: Martin KaFai Lau 
Fixes: bd16dee66ae4 ("bpf: Add BTF_KIND_DECL_TAG typedef support")
Reported-by: syzbot+d8bd751aef7c6b39a344@syzkaller.appspotmail.com
Signed-off-by: Stanislav Fomichev 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/r/20221015002444.2680969-2-sdf@google.com
Signed-off-by: Martin KaFai Lau