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/* Copyright (c) 2017 Facebook
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License as published by the Free Software Foundation.
*/
#include <linux/bpf.h>
#include <linux/version.h>
#include <bpf/bpf_helpers.h>
SEC("cgroup/dev")
int bpf_prog1(struct bpf_cgroup_dev_ctx *ctx)
{
short type = ctx->access_type & 0xFFFF;
#ifdef DEBUG
short access = ctx->access_type >> 16;
char fmt[] = " %d:%d \n";
switch (type) {
case BPF_DEVCG_DEV_BLOCK:
fmt[0] = 'b';
break;
case BPF_DEVCG_DEV_CHAR:
fmt[0] = 'c';
break;
default:
fmt[0] = '?';
break;
}
if (access & BPF_DEVCG_ACC_READ)
fmt[8] = 'r';
if (access & BPF_DEVCG_ACC_WRITE)
fmt[9] = 'w';
if (access & BPF_DEVCG_ACC_MKNOD)
fmt[10] = 'm';
bpf_trace_printk(fmt, sizeof(fmt), ctx->major, ctx->minor);
#endif
/* Allow access to /dev/zero and /dev/random.
* Forbid everything else.
*/
if (ctx->major != 1 || type != BPF_DEVCG_DEV_CHAR)
return 0;
switch (ctx->minor) {
case 5: /* 1:5 /dev/zero */
case 9: /* 1:9 /dev/urandom */
return 1;
}
return 0;
}
char _license[] SEC("license") = "GPL";
__u32 _version SEC("version") = LINUX_VERSION_CODE;
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