495d2d8133
GCC's -Wall includes -Wsign-compare while clang does not. Since BPF programs are built with clang we need to add this flag explicitly to catch problematic comparisons like: int i = -1; unsigned int j = 1; if (i < j) // this is false. long i = -1; unsigned int j = 1; if (i < j) // this is true. C standard for reference: - If either operand is unsigned long the other shall be converted to unsigned long. - Otherwise, if one operand is a long int and the other unsigned int, then if a long int can represent all the values of an unsigned int, the unsigned int shall be converted to a long int; otherwise both operands shall be converted to unsigned long int. - Otherwise, if either operand is long, the other shall be converted to long. - Otherwise, if either operand is unsigned, the other shall be converted to unsigned. Unfortunately clang's -Wsign-compare is very noisy. It complains about (s32)a == (u32)b which is safe and doen't have surprising behavior. This patch fixes some of the issues. It needs a follow up to fix the rest. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Jiri Olsa <jolsa@kernel.org> Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/bpf/20231226191148.48536-2-alexei.starovoitov@gmail.com
48 lines
1.1 KiB
C
48 lines
1.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
|
|
|
|
#include "vmlinux.h"
|
|
#include <bpf/bpf_helpers.h>
|
|
#include <bpf/bpf_tracing.h>
|
|
#include "bpf_kfuncs.h"
|
|
|
|
char _license[] SEC("license") = "GPL";
|
|
|
|
#ifndef SHA256_DIGEST_SIZE
|
|
#define SHA256_DIGEST_SIZE 32
|
|
#endif
|
|
|
|
#define SIZEOF_STRUCT_FSVERITY_DIGEST 4 /* sizeof(struct fsverity_digest) */
|
|
|
|
char expected_digest[SIZEOF_STRUCT_FSVERITY_DIGEST + SHA256_DIGEST_SIZE];
|
|
char digest[SIZEOF_STRUCT_FSVERITY_DIGEST + SHA256_DIGEST_SIZE];
|
|
__u32 monitored_pid;
|
|
__u32 got_fsverity;
|
|
__u32 digest_matches;
|
|
|
|
SEC("lsm.s/file_open")
|
|
int BPF_PROG(test_file_open, struct file *f)
|
|
{
|
|
struct bpf_dynptr digest_ptr;
|
|
__u32 pid;
|
|
int ret;
|
|
int i;
|
|
|
|
pid = bpf_get_current_pid_tgid() >> 32;
|
|
if (pid != monitored_pid)
|
|
return 0;
|
|
|
|
bpf_dynptr_from_mem(digest, sizeof(digest), 0, &digest_ptr);
|
|
ret = bpf_get_fsverity_digest(f, &digest_ptr);
|
|
if (ret < 0)
|
|
return 0;
|
|
got_fsverity = 1;
|
|
|
|
for (i = 0; i < (int)sizeof(digest); i++) {
|
|
if (digest[i] != expected_digest[i])
|
|
return 0;
|
|
}
|
|
|
|
digest_matches = 1;
|
|
return 0;
|
|
}
|