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  1. 14 Jul, 2023 35 commits
  3. 13 Jul, 2023 5 commits
    • Yafang Shao's avatar
      selftests/bpf: Add selftest for PTR_UNTRUSTED · 1cd0e771
      Yafang Shao authored 
      Add a new selftest to check the PTR_UNTRUSTED condition. Below is the
result,

 #160     ptr_untrusted:OK
Signed-off-by: default avatarYafang Shao <laoar.shao@gmail.com>
Link: https://lore.kernel.org/r/20230713025642.27477-5-laoar.shao@gmail.comSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      1cd0e771
    • Yafang Shao's avatar
      bpf: Fix an error in verifying a field in a union · 33937607
      Yafang Shao authored 
      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: 7e3617a7 ("bpf: Add array support to btf_struct_access")
Signed-off-by: default avatarYafang Shao <laoar.shao@gmail.com>
Link: https://lore.kernel.org/r/20230713025642.27477-4-laoar.shao@gmail.comSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      33937607
    • Yafang Shao's avatar
      selftests/bpf: Add selftests for nested_trust · d2284d68
      Yafang Shao authored 
      Add selftests for nested_strust to check whehter PTR_UNTRUSTED is cleared
as expected, the result as follows:

 #141/1   nested_trust/test_read_cpumask:OK
 #141/2   nested_trust/test_skb_field:OK                    <<<<
 #141/3   nested_trust/test_invalid_nested_user_cpus:OK
 #141/4   nested_trust/test_invalid_nested_offset:OK
 #141/5   nested_trust/test_invalid_skb_field:OK            <<<<
 #141     nested_trust:OK

The #141/2 and #141/5 are newly added.
Signed-off-by: default avatarYafang Shao <laoar.shao@gmail.com>
Link: https://lore.kernel.org/r/20230713025642.27477-3-laoar.shao@gmail.comSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      d2284d68
    • Yafang Shao's avatar
      bpf: Fix an error around PTR_UNTRUSTED · 7ce4dc3e
      Yafang Shao authored 
      Per discussion with Alexei, the PTR_UNTRUSTED flag should not been
cleared when we start to walk a new struct, because the struct in
question may be a struct nested in a union. We should also check and set
this flag before we walk its each member, in case itself is a union.
We will clear this flag if the field is BTF_TYPE_SAFE_RCU_OR_NULL.

Fixes: 6fcd486b ("bpf: Refactor RCU enforcement in the verifier.")
Signed-off-by: default avatarYafang Shao <laoar.shao@gmail.com>
Link: https://lore.kernel.org/r/20230713025642.27477-2-laoar.shao@gmail.comSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      7ce4dc3e
    • Alexei Starovoitov's avatar
      Merge branch 'bpf-x86-allow-function-arguments-up-to-12-for-tracing' · f892cac2
      Alexei Starovoitov authored 
      Menglong Dong says:

====================
bpf, x86: allow function arguments up to 12 for TRACING

From: Menglong Dong <imagedong@tencent.com>

For now, the BPF program of type BPF_PROG_TYPE_TRACING can only be used
on the kernel functions whose arguments count less than or equal to 6, if
not considering '> 8 bytes' struct argument. This is not friendly at all,
as too many functions have arguments count more than 6. According to the
current kernel version, below is a statistics of the function arguments
count:

argument count | function count
7              | 704
8              | 270
9              | 84
10             | 47
11             | 47
12             | 27
13             | 22
14             | 5
15             | 0
16             | 1

Therefore, let's enhance it by increasing the function arguments count
allowed in arch_prepare_bpf_trampoline(), for now, only x86_64.

In the 1st patch, we save/restore regs with BPF_DW size to make the code
in save_regs()/restore_regs() simpler.

In the 2nd patch, we make arch_prepare_bpf_trampoline() support to copy
function arguments in stack for x86 arch. Therefore, the maximum
arguments can be up to MAX_BPF_FUNC_ARGS for FENTRY, FEXIT and
MODIFY_RETURN. Meanwhile, we clean the potential garbage value when we
copy the arguments on-stack.

And the 3rd patch is for the testcases of the this series.

Changes since v9:
- fix the failed test cases of trampoline_count and get_func_args_test
  in the 3rd patch

Changes since v8:
- change the way to test fmod_ret in the 3rd patch

Changes since v7:
- split the testcases, and add fentry_many_args/fexit_many_args to
  DENYLIST.aarch64 in 3rd patch

Changes since v6:
- somit nits from commit message and comment in the 1st patch
- remove the inline in get_nr_regs() in the 1st patch
- rename some function and various in the 1st patch

Changes since v5:
- adjust the commit log of the 1st patch, avoiding confusing people that
  bugs exist in current code
- introduce get_nr_regs() to get the space that used to pass args on
  stack correct in the 2nd patch
- add testcases to tracing_struct.c instead of fentry_test.c and
  fexit_test.c

Changes since v4:
- consider the case of the struct in arguments can't be hold by regs
- add comment for some code
- add testcases for MODIFY_RETURN
- rebase to the latest

Changes since v3:
- try make the stack pointer 16-byte aligned. Not sure if I'm right :)
- introduce clean_garbage() to clean the grabage when argument count is 7
- use different data type in bpf_testmod_fentry_test{7,12}
- add testcase for grabage values in ctx

Changes since v2:
- keep MAX_BPF_FUNC_ARGS still
- clean garbage value in upper bytes in the 2nd patch
- move bpf_fentry_test{7,12} to bpf_testmod.c and rename them to
  bpf_testmod_fentry_test{7,12} meanwhile in the 3rd patch

Changes since v1:
- change the maximun function arguments to 14 from 12
- add testcases (Jiri Olsa)
- instead EMIT4 with EMIT3_off32 for "lea" to prevent overflow
====================

Link: https://lore.kernel.org/r/20230713040738.1789742-1-imagedong@tencent.comSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      f892cac2
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