[krbdev.mit.edu #9109] Re: memory leak on macos

[Anthony Sottile via RT]

<URL: http://kerborg-prod-app-1.mit.edu/rt/Ticket/Display.html?id=9109 >

here is a patch which fixes the bug:

```diff
--- lib/krb5/ccache/cc_api_macos.c.old 2024-01-10 16:14:19
+++ lib/krb5/ccache/cc_api_macos.c 2024-01-10 16:14:43
@@ -218,8 +218,10 @@
         xpc_release(request);
     if (reply != NULL)
         xpc_release(reply);
-    if (conn != NULL)
+    if (conn != NULL) {
         xpc_connection_cancel(conn);
+        xpc_release(conn);
+    }
     return ret;
 }
 ```

On Wed, Jan 10, 2024 at 2:46 PM Anthony Sottile
<anthony.sottile at sentry.io> wrote:
>
> hello, I've found what I believe to be a memory leak on macos -- I've
> tried to narrow it down to a simple reproduction:
>
> ```c
> #include <stdbool.h>
> #include <stdio.h>
> #include <gssapi.h>
>
> int main(void) {
>     for (int i = 0; i < 10; i += 1) {
>         gss_cred_id_t cred = 0;
>         OM_uint32 minor = 0;
>         OM_uint32 ret = gss_acquire_cred(
>             &minor, GSS_C_NO_NAME, 0, GSS_C_NO_OID_SET,
>             GSS_C_INITIATE, &cred, NULL, NULL
>         );
>         if (ret == GSS_S_COMPLETE) {
>             printf("no error\n");
>             gss_release_cred(&minor, &cred);
>         } else {
>             printf("got error: %d\n", ret);
>         }
>     }
> }
> ```
>
> compiled using:
>
> ```bash
> gcc $(PKG_CONFIG_PATH=/opt/homebrew/Cellar/krb5/1.21.2/lib/pkgconfig/
> pkg-config krb5-gssapi --cflags --libs) t.c
> ```
>
> leaks shown using:
>
> ```bash
> leaks --atExit -- ./a.out
> ```
>
> note: I don't have gss set up in any way so the expected path of my
> program above is the error case:
>
> ```console
> $ ./a.out
> got error: 458752
> got error: 458752
> got error: 458752
> got error: 458752
> got error: 458752
> got error: 458752
> got error: 458752
> got error: 458752
> got error: 458752
> got error: 458752
> ```
>
>
>
> this leak is the important one (the other is sort of expected, a
> global error message retrievable later and is not per-call):
>
> ```
>
> STACK OF 8 INSTANCES OF 'ROOT CYCLE: <OS_xpc_connection>':
> 19  dyld                                  0x1822eff28 start + 2236
> 18  a.out                                 0x102af7f00 main + 88
> 17  libgssapi_krb5.2.2.dylib              0x102bdac2c gss_acquire_cred + 36
> 16  libgssapi_krb5.2.2.dylib              0x102bdadc8
> gss_acquire_cred_from + 400
> 15  libgssapi_krb5.2.2.dylib              0x102bdb180 gss_add_cred_from + 624
> 14  libgssapi_krb5.2.2.dylib              0x102bf8d30
> spnego_gss_acquire_cred_from + 128
> 13  libgssapi_krb5.2.2.dylib              0x102bf8e8c get_available_mechs + 228
> 12  libgssapi_krb5.2.2.dylib              0x102bdadc8
> gss_acquire_cred_from + 400
> 11  libgssapi_krb5.2.2.dylib              0x102bdb180 gss_add_cred_from + 624
> 10  libgssapi_krb5.2.2.dylib              0x102be919c acquire_cred_from + 68
> 9   libgssapi_krb5.2.2.dylib              0x102be9894
> acquire_cred_context + 1664
> 8   libkrb5.3.3.dylib                     0x102cf1a70
> krb5_cccol_have_content + 92
> 7   libkrb5.3.3.dylib                     0x102cf1788
> krb5_cccol_cursor_next + 76
> 6   libkrb5.3.3.dylib                     0x102cf44dc
> api_macos_ptcursor_next + 240
> 5   libkrb5.3.3.dylib                     0x102cf49d4 get_primary_name + 124
> 4   libxpc.dylib                          0x182388850
> xpc_connection_create_mach_service + 40
> 3   libxpc.dylib                          0x182398f80
> _xpc_connection_create + 136
> 2   libdispatch.dylib                     0x182497838
> _os_object_alloc_realized + 32
> 1   libobjc.A.dylib                       0x1822abe00 class_createInstance + 64
> 0   libsystem_malloc.dylib                0x182488eb0
> _malloc_zone_calloc_instrumented_or_legacy + 92
> ====
>     47 (5.98K) << TOTAL >>
>       ----
>       6 (784 bytes) ROOT CYCLE: <OS_xpc_connection 0x13e0065e0> [240]
> "com.apple.GSSCred" (from libkrb5.3.3.dylib) pid 599 [GSSCred]
>          3 (368 bytes) ROOT CYCLE: <OS_dispatch_mach 0x13e008400>
> [160]  "com.apple.GSSCred" (from libkrb5.3.3.dylib)
>             1 (64 bytes) ROOT CYCLE: <calloc in _dispatch_unote_create
> 0x13e0076f0> [64]
>                CYCLE BACK TO <OS_xpc_connection 0x13e0065e0> [240]
> "com.apple.GSSCred" (from libkrb5.3.3.dylib) pid 599 [GSSCred]
>             1 (144 bytes) <calloc in _dispatch_unote_create 0x13e0084a0> [144]
>          2 (176 bytes) <calloc in _xpc_connection_cancel 0x13e0066d0> [32]
>             1 (144 bytes) <malloc in _vasprintf 0x13e0088b0> [144]
> ```
>
> seemingly from this code here:
> https://github.com/krb5/krb5/blob/ec71ac1cabbb3926f8ffaf71e1ad007e4e56e0e5/src/lib/krb5/ccache/cc_api_macos.c#L161-L224
>
> I'm on macos 13.5.2 arm64 and using krb5 1.21.2 from homebrew
>
> ```
> $ uname -a
>
> Darwin FJJ4YYCWYX.local 22.6.0 Darwin Kernel Version 22.6.0: Wed Jul
> 5 22:22:05 PDT 2023; root:xnu-8796.141.3~6/RELEASE_ARM64_T6000 arm64
> arm Darwin
> ```
>
> anthony