c++ - libssh:简单实现中丢失的内存

Question

我正在尝试一个非常简单的 libssh 实现，但 valgrind 显示内存泄漏。

代码是:

#include <libssh/libssh.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
int main()
{
        ssh_session my_ssh_session = ssh_new();
        int port = 22;
        int rc, state;
        const char *ip = "192.168.125.241";
        char *password;
        if (my_ssh_session == NULL)
                exit(-1);
        ssh_options_set(my_ssh_session, SSH_OPTIONS_HOST, ip);
        ssh_options_set(my_ssh_session, SSH_OPTIONS_PORT, &port);
        rc = ssh_connect(my_ssh_session);
        if (rc != SSH_OK)
        {
                fprintf(stderr, "Error connecting to localhost: %s\n",
                ssh_get_error(my_ssh_session));
                exit(-1);
        }

        state = ssh_is_server_known(my_ssh_session);
        if(state == SSH_SERVER_KNOWN_OK)
                printf("already added\n");
        else
                printf("require addition\n");

        rc = ssh_userauth_password(my_ssh_session, "rohit", "password");
        if (rc != SSH_AUTH_SUCCESS)
        {
                fprintf(stderr, "Error authenticating with password: %s\n",
                ssh_get_error(my_ssh_session));
                ssh_disconnect(my_ssh_session);
                ssh_free(my_ssh_session);
                exit(-1);
        }
        ssh_disconnect(my_ssh_session);
        ssh_free(my_ssh_session);
}

编译:

gcc sshex.c -lssh

VALGRIND 运行:

root@rohit-Precision-T1500:/# valgrind --tool=memcheck --leak-check=full --show-leak-kinds=all --show-reachable=no ./a.out 
==1937== Memcheck, a memory error detector
==1937== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==1937== Using Valgrind-3.10.0.SVN and LibVEX; rerun with -h for copyright info
==1937== Command: ./a.out
==1937== 
yahoo
==1937== 
==1937== HEAP SUMMARY:
==1937==     in use at exit: 14,256 bytes in 521 blocks
==1937==   total heap usage: 1,339 allocs, 818 frees, 92,442 bytes allocated
==1937== 
==1937== 24 bytes in 1 blocks are indirectly lost in loss record 507 of 520
==1937==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1937==    by 0x56AAD32: CRYPTO_malloc (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E3A59: BN_new (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E3F07: BN_bin2bn (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x4E6079B: pki_signature_from_blob (pki_crypto.c:1384)
==1937==    by 0x4E599F9: ssh_pki_import_signature_blob (pki.c:1262)
==1937==    by 0x4E59A77: ssh_pki_signature_verify_blob (pki.c:1281)
==1937==    by 0x4E578DE: ssh_packet_newkeys (packet_cb.c:186)
==1937==    by 0x4E56E6F: ssh_packet_process (packet.c:422)
==1937==    by 0x4E57374: ssh_packet_socket_callback (packet.c:326)
==1937==    by 0x4E573B3: ssh_packet_socket_callback (packet.c:336)
==1937==    by 0x4E5D951: ssh_socket_pollcallback (socket.c:290)
==1937== 
==1937== 24 bytes in 1 blocks are indirectly lost in loss record 508 of 520
==1937==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1937==    by 0x56AAD32: CRYPTO_malloc (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E3A59: BN_new (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E3F07: BN_bin2bn (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x4E607EC: pki_signature_from_blob (pki_crypto.c:1405)
==1937==    by 0x4E599F9: ssh_pki_import_signature_blob (pki.c:1262)
==1937==    by 0x4E59A77: ssh_pki_signature_verify_blob (pki.c:1281)
==1937==    by 0x4E578DE: ssh_packet_newkeys (packet_cb.c:186)
==1937==    by 0x4E56E6F: ssh_packet_process (packet.c:422)
==1937==    by 0x4E57374: ssh_packet_socket_callback (packet.c:326)
==1937==    by 0x4E573B3: ssh_packet_socket_callback (packet.c:336)
==1937==    by 0x4E5D951: ssh_socket_pollcallback (socket.c:290)
==1937== 
==1937== 32 bytes in 1 blocks are indirectly lost in loss record 511 of 520
==1937==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1937==    by 0x56AAD32: CRYPTO_malloc (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E35E6: ??? (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E3AD4: bn_expand2 (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E3ECF: BN_bin2bn (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x4E6079B: pki_signature_from_blob (pki_crypto.c:1384)
==1937==    by 0x4E599F9: ssh_pki_import_signature_blob (pki.c:1262)
==1937==    by 0x4E59A77: ssh_pki_signature_verify_blob (pki.c:1281)
==1937==    by 0x4E578DE: ssh_packet_newkeys (packet_cb.c:186)
==1937==    by 0x4E56E6F: ssh_packet_process (packet.c:422)
==1937==    by 0x4E57374: ssh_packet_socket_callback (packet.c:326)
==1937==    by 0x4E573B3: ssh_packet_socket_callback (packet.c:336)
==1937== 
==1937== 32 bytes in 1 blocks are indirectly lost in loss record 512 of 520
==1937==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1937==    by 0x56AAD32: CRYPTO_malloc (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E35E6: ??? (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E3AD4: bn_expand2 (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E3ECF: BN_bin2bn (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x4E607EC: pki_signature_from_blob (pki_crypto.c:1405)
==1937==    by 0x4E599F9: ssh_pki_import_signature_blob (pki.c:1262)
==1937==    by 0x4E59A77: ssh_pki_signature_verify_blob (pki.c:1281)
==1937==    by 0x4E578DE: ssh_packet_newkeys (packet_cb.c:186)
==1937==    by 0x4E56E6F: ssh_packet_process (packet.c:422)
==1937==    by 0x4E57374: ssh_packet_socket_callback (packet.c:326)
==1937==    by 0x4E573B3: ssh_packet_socket_callback (packet.c:336)
==1937== 
==1937== 48 bytes in 2 blocks are definitely lost in loss record 513 of 520
==1937==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1937==    by 0x56AAD32: CRYPTO_malloc (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x56E3A59: BN_new (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x574C358: ??? (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x5750B1A: ??? (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x5750BC5: ??? (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x5750D79: ASN1_item_new (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x4E60734: pki_signature_from_blob (pki_crypto.c:1347)
==1937==    by 0x4E599F9: ssh_pki_import_signature_blob (pki.c:1262)
==1937==    by 0x4E59A77: ssh_pki_signature_verify_blob (pki.c:1281)
==1937==    by 0x4E578DE: ssh_packet_newkeys (packet_cb.c:186)
==1937==    by 0x4E56E6F: ssh_packet_process (packet.c:422)
==1937== 
==1937== 128 (16 direct, 112 indirect) bytes in 1 blocks are definitely lost in loss record 516 of 520
==1937==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1937==    by 0x56AAD32: CRYPTO_malloc (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x5750D0B: ??? (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x5750D79: ASN1_item_new (in /lib/x86_64-linux-gnu/libcrypto.so.1.0.0)
==1937==    by 0x4E60734: pki_signature_from_blob (pki_crypto.c:1347)
==1937==    by 0x4E599F9: ssh_pki_import_signature_blob (pki.c:1262)
==1937==    by 0x4E59A77: ssh_pki_signature_verify_blob (pki.c:1281)
==1937==    by 0x4E578DE: ssh_packet_newkeys (packet_cb.c:186)
==1937==    by 0x4E56E6F: ssh_packet_process (packet.c:422)
==1937==    by 0x4E57374: ssh_packet_socket_callback (packet.c:326)
==1937==    by 0x4E573B3: ssh_packet_socket_callback (packet.c:336)
==1937==    by 0x4E5D951: ssh_socket_pollcallback (socket.c:290)
==1937== 
==1937== LEAK SUMMARY:
==1937==    definitely lost: 64 bytes in 3 blocks
==1937==    indirectly lost: 112 bytes in 4 blocks
==1937==      possibly lost: 0 bytes in 0 blocks
==1937==    still reachable: 14,080 bytes in 514 blocks
==1937==         suppressed: 0 bytes in 0 blocks
==1937== Reachable blocks (those to which a pointer was found) are not shown.

直接运行:

root@rohit-Precision-T1500:/# gcc sshex.c -lssh
root@rohit-Precision-T1500:/# ./a.out 
already added
root@rohit-Precision-T1500:/# 

Linux 版本:

root@rohit-Precision-T1500:/# uname -a
Linux rohit-Precision-T1500 3.13.0-43-generic #72-Ubuntu SMP Mon Dec 8 19:35:06 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

我已经尝试过这个。如果我删除函数 ssh_connect() (当然还有其他后续函数)，那么我就不会得到任何泄漏。因此，泄漏一定是由这个函数引发的。但是在我的小程序中，我使用了函数ssh_disconnect()来释放ssh_connect()分配的内存。那么，我怎样才能确定释放内存呢？

我想在我的软件中使用 SCP 功能，这将是一个长期存在的过程。因此，内存泄漏将成为一个严重的问题。根据我的理解，泄漏与 libcrypto 库有关，这可能不是 libssh 的泄漏。如果是或不是，消除这些泄漏的解决方案是什么？我哪里做错了？

Answer 1

正如我所料，事情发生了。这可能是 libcrypto 中的错误。我在 RHEL 6.5 中运行我的程序，valgrind 没有显示任何泄漏。

这是输出的片段:

[root@demo-hadoop test]# gcc sshex.c -lssh
[root@demo-hadoop test]# valgrind --tool=memcheck ./a.out 
==23636== Memcheck, a memory error detector
==23636== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.
==23636== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info
==23636== Command: ./a.out
==23636== 
already added
==23636== 
==23636== HEAP SUMMARY:
==23636==     in use at exit: 15,304 bytes in 532 blocks
==23636==   total heap usage: 1,067 allocs, 535 frees, 82,199 bytes allocated
==23636== 
==23636== LEAK SUMMARY:
==23636==    definitely lost: 0 bytes in 0 blocks
==23636==    indirectly lost: 0 bytes in 0 blocks
==23636==      possibly lost: 0 bytes in 0 blocks
==23636==    still reachable: 15,304 bytes in 532 blocks
==23636==         suppressed: 0 bytes in 0 blocks
==23636== Rerun with --leak-check=full to see details of leaked memory
==23636== 
==23636== For counts of detected and suppressed errors, rerun with: -v
==23636== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 6 from 6)
[root@demo-hadoop test]# 
[root@demo-hadoop test]# 
[root@demo-hadoop test]# uname -a
Linux demo-hadoop 2.6.32-431.el6.x86_64 #1 SMP Sun Nov 10 22:19:54 EST 2013 x86_64 x86_64 x86_64 GNU/Linux

所以，当然，这不是 libssh 中的错误。