处理不受setrlimit限制的资源 [英] Processes resources not limited by setrlimit

问题描述

我写了一个简单的程序来将其数据大小限制为65Kb，并验证是否我分配的虚拟内存超过65Kb，并且从逻辑上讲，如果我做的所有正确(如下所示)，malloc调用应该失败，不是它吗?

I wrote a simple program to restrict it's data size to 65Kb and to verify the same i am allocating a dummy memory of more than 65Kb and logically if i am doing all correct (as below) malloc call should fail, isn't it?

#include <sys/resource.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>

int main (int argc, char *argv[])
{
  struct rlimit limit;


  /* Get max data size . */
  if (getrlimit(RLIMIT_DATA, &limit) != 0) {
    printf("getrlimit() failed with errno=%d\n", errno);
    return 1;
  }

  printf("The soft limit is %lu\n", limit.rlim_cur);
  printf("The hard limit is %lu\n", limit.rlim_max);

  limit.rlim_cur = 65 * 1024;
  limit.rlim_max = 65 * 1024;

  if (setrlimit(RLIMIT_DATA, &limit) != 0) {
    printf("setrlimit() failed with errno=%d\n", errno);
    return 1;
  }

  if (getrlimit(RLIMIT_DATA, &limit) != 0) {
    printf("getrlimit() failed with errno=%d\n", errno);
    return 1;
  }

  printf("The soft limit is %lu\n", limit.rlim_cur);
  printf("The hard limit is %lu\n", limit.rlim_max);
  system("bash -c 'ulimit -a'");
    int *new2 = NULL;
    new2 = malloc(66666666);
    if (new2 == NULL)
    {
        printf("malloc failed\n");
        return;
    }
    else
    {
        printf("success\n");
    }

  return 0;
}

令人惊讶的是，输出是这样的-

Surprisingly, the ouput is something like this -

The soft limit is 4294967295
The hard limit is 4294967295
The soft limit is 66560
The hard limit is 66560
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) 65
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 14895
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 14895
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited
success

我以任何方式做错了吗? 请删除您的输入. 谢谢！

Am i doing wrong in any way? Please drop your inputs. Thanks!

推荐答案

来自

RLIMIT_DATA

RLIMIT_DATA

流程数据段的最大大小(已初始化 数据，未初始化的数据和堆).此限制会影响通话 到brk(2)和sbrk(2)，它们在失败时会出现错误ENOMEM 遇到此资源的软限制.

The maximum size of the process's data segment (initialized data, uninitialized data, and heap). This limit affects calls to brk(2) and sbrk(2), which fail with the error ENOMEM upon encountering the soft limit of this resource.

具体地说，该资源不适用于通过mmap获得的内存.在内部，malloc使用各种机制来获取新的内存.在这种情况下，您会发现它使用的是mmap，而不是sbrk或brk.您可以通过使用strace转储程序中的系统调用来验证这一点.

Specifically, that resource does not apply to memory obtained via mmap. Internally malloc uses various mechanisms for obtaining new memory. In this case you will find that it used mmap and not sbrk or brk. You can verify this by dumping the system calls from your program with strace.

要实现所需的目标，请使用RLIMIT_AS资源.

To achieve what you want use the RLIMIT_AS resource instead.

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