[lxc-devel] Question: Some confusion about lxc-test-apparmor #2206

[Hongzhi, Song]

I use the same lxc-test-apparmor on Ubuntu16.04. And part of files 
listed in files_to_deny[] also exit in Ubunut system, but the results pass.


On 2018年03月07日 17:00, Hongzhi, Song wrote:
>
> Dose it mean that I should unenable the files listed in 
> files_to_deny[], when using lxc-test-apparmor ?
>
>
> On 2018年03月07日 16:57, Hongzhi, Song wrote:
>>
>> I have some confusion about source code of lxc-test-apparmor defined 
>> in 'lxc/src/tests/aa.c'.
>>
>>   * The output of||
>>   * |lxc-test-apparmor|
>>
>> |passed with /sys/kernel/uevent_helper passed with 
>> /proc/sys/fs/file-nr failed - opened /sys/kernel/mm/ksm/pages_to_scan |
>>
>>   * |ls -l /sys/kernel/uevent_helper|
>>   * |ls -l /sys/kernel/mm/ksm/pages_to_scan|
>>
>> |root at intel-x86-64:# ls -l /sys/kernel/uevent_helper ls: cannot access 
>> '/sys/kernel/uevent_helper': No such file or directory 
>> root at intel-x86-64:# ls -l /sys/kernel/mm/ksm/pages_to_scan -rw-r--r-- 
>> 1 root root 4096 Mar 6 19:17 /sys/kernel/mm/ksm/pages_to_scan |
>>
>>
>>         Issue description
>>
>> As shown above, /sys/kernel/mm/ksm/pages_to_scan is exist, and can be 
>> opened. But error message prompts that fail to open it.
>> I refer to source code lxc/src/tests/aa.c, branch master.
>>
>> |108 char *files_to_deny[] = { 109 "/sys/kernel/uevent_helper", 110 
>> "/proc/sys/fs/file-nr", 111 "/sys/kernel/mm/ksm/pages_to_scan", 112 
>> "/proc/sys/kernel/sysrq", 113 NULL }; |
>> |115 static bool test_aa_policy(struct lxc_container *c) 116 { 117 int 
>> i, ret; 118 119 for (i = 0; files_to_deny[i]; i++) { 120 ret = 
>> do_test_file_open(c, files_to_deny[i]); 121 if (ret < 0) { 122 
>> fprintf(stderr, "attach failed; skipping test\n"); 123 return true; 
>> 124 } 125 if (ret > 0) { 126 fprintf(stderr, "failed - opened %s\n", 
>> 127 files_to_deny[i]); 128 return false; 129 } 130 fprintf(stderr, 
>> "passed with %s\n", files_to_deny[i]); 131 } ...... |
>> |63 static int do_test_file_open(struct lxc_container *c, char *fnam) 
>> 64 { 65 int fret = -1; 66 int ret; 67 pid_t pid; 68 int pipefd[2]; 69 
>> char result[1024]; 70 lxc_attach_options_t attach_options = 
>> LXC_ATTACH_OPTIONS_DEFAULT; 71 72 ret = pipe(pipefd); 73 if (ret < 0) 
>> { 74 fprintf(stderr, "pipe failed %d\n", ret); 75 return fret; 76 } 
>> 77 attach_options.stdout_fd = pipefd[1]; 78 
>> attach_options.attach_flags &= 
>> ~(LXC_ATTACH_LSM_EXEC|LXC_ATTACH_DROP_CAPABILITIES); 79 
>> attach_options.attach_flags |= LXC_ATTACH_LSM_NOW; 80 ret = 
>> c->attach(c, test_attach_write_file, fnam, &attach_options, &pid); 
>> ...... 85 86 ret = read(pipefd[0], result, sizeof(result)-1); 87 if 
>> (ret < 0) { 88 fprintf(stderr, "read failed %d\n", ret); 89 goto 
>> err2; 90 } 91 92 fret = 1; 93 if (strncmp(result, "no", 2) == 0) 94 
>> fret = 0; ...... 101 return fret; 102 } |
>> |41 static int test_attach_write_file(void* payload) 42 { 43 char 
>> *fnam = payload; 44 FILE *f; 45 46 f = fopen(fnam, "w"); 47 if (f) { 
>> 48 printf("yes\n"); 49 fclose(f); 50 fflush(NULL); 51 return 1; 52 } 
>> 53 printf("no\n"); 54 fflush(NULL); 55 return 0; 56 } |
>>
>> Line46-48: If open interfaces successfully listed in files_to_deny[], 
>> Line108, printf 'yes' into pipe[1].
>> Line86: And then pipe[0] reads out 'yes'.
>> Line92-101: If result is 'yes', do_test_file_open() will return 1.
>> Line125-128: If the return of do_test_file_open() is 1, then fprintf( 
>> failed open).
>> So can anyone tell me why files listed in files_to_deny[] exit but 
>> print fail.
>>
>> Thanks.
>>
>>
>> ||
>

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