s3: Fix Coverity ID 242710 Untrusted pointer read
[Samba/gebeck_regimport.git] / lib / util / talloc_stack.c
blob16e9d745d347fe340b7fd40b3e027dc358934e5a
1 /*
2 Unix SMB/CIFS implementation.
3 Implement a stack of talloc contexts
4 Copyright (C) Volker Lendecke 2007
5 Copyright (C) Jeremy Allison 2009 - made thread safe.
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
23 * Implement a stack of talloc frames.
25 * When a new talloc stackframe is allocated with talloc_stackframe(), then
26 * the TALLOC_CTX returned with talloc_tos() is reset to that new
27 * frame. Whenever that stack frame is TALLOC_FREE()'ed, then the reverse
28 * happens: The previous talloc_tos() is restored.
30 * This API is designed to be robust in the sense that if someone forgets to
31 * TALLOC_FREE() a stackframe, then the next outer one correctly cleans up and
32 * resets the talloc_tos().
34 * This robustness feature means that we can't rely on a linked list with
35 * talloc destructors because in a hierarchy of talloc destructors the parent
36 * destructor is called before its children destructors. The child destructor
37 * called after the parent would set the talloc_tos() to the wrong value.
40 #include "includes.h"
42 struct talloc_stackframe {
43 int talloc_stacksize;
44 int talloc_stack_arraysize;
45 TALLOC_CTX **talloc_stack;
49 * In the single threaded case this is a pointer
50 * to the global talloc_stackframe. In the MT-case
51 * this is the pointer to the thread-specific key
52 * used to look up the per-thread talloc_stackframe
53 * pointer.
56 static void *global_ts;
58 /* Variable to ensure TLS value is only initialized once. */
59 static smb_thread_once_t ts_initialized = SMB_THREAD_ONCE_INIT;
61 static void talloc_stackframe_init(void * unused)
63 if (SMB_THREAD_CREATE_TLS("talloc_stackframe", global_ts)) {
64 smb_panic("talloc_stackframe_init create_tls failed");
68 static struct talloc_stackframe *talloc_stackframe_create(void)
70 #if defined(PARANOID_MALLOC_CHECKER)
71 #ifdef calloc
72 #undef calloc
73 #endif
74 #endif
75 struct talloc_stackframe *ts = (struct talloc_stackframe *)calloc(
76 1, sizeof(struct talloc_stackframe));
77 #if defined(PARANOID_MALLOC_CHECKER)
78 #define calloc(n, s) __ERROR_DONT_USE_MALLOC_DIRECTLY
79 #endif
81 if (!ts) {
82 smb_panic("talloc_stackframe_init malloc failed");
85 SMB_THREAD_ONCE(&ts_initialized, talloc_stackframe_init, NULL);
87 if (SMB_THREAD_SET_TLS(global_ts, ts)) {
88 smb_panic("talloc_stackframe_init set_tls failed");
90 return ts;
93 static int talloc_pop(TALLOC_CTX *frame)
95 struct talloc_stackframe *ts =
96 (struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
97 int i;
99 for (i=ts->talloc_stacksize-1; i>0; i--) {
100 if (frame == ts->talloc_stack[i]) {
101 break;
103 TALLOC_FREE(ts->talloc_stack[i]);
106 ts->talloc_stack[i] = NULL;
107 ts->talloc_stacksize = i;
108 return 0;
112 * Create a new talloc stack frame.
114 * When free'd, it frees all stack frames that were created after this one and
115 * not explicitly freed.
118 static TALLOC_CTX *talloc_stackframe_internal(size_t poolsize)
120 TALLOC_CTX **tmp, *top, *parent;
121 struct talloc_stackframe *ts =
122 (struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
124 if (ts == NULL) {
125 ts = talloc_stackframe_create();
128 if (ts->talloc_stack_arraysize < ts->talloc_stacksize + 1) {
129 tmp = talloc_realloc(NULL, ts->talloc_stack, TALLOC_CTX *,
130 ts->talloc_stacksize + 1);
131 if (tmp == NULL) {
132 goto fail;
134 ts->talloc_stack = tmp;
135 ts->talloc_stack_arraysize = ts->talloc_stacksize + 1;
138 if (ts->talloc_stacksize == 0) {
139 parent = ts->talloc_stack;
140 } else {
141 parent = ts->talloc_stack[ts->talloc_stacksize-1];
144 if (poolsize) {
145 top = talloc_pool(parent, poolsize);
146 } else {
147 top = talloc_new(parent);
150 if (top == NULL) {
151 goto fail;
154 talloc_set_destructor(top, talloc_pop);
156 ts->talloc_stack[ts->talloc_stacksize++] = top;
157 return top;
159 fail:
160 smb_panic("talloc_stackframe failed");
161 return NULL;
164 TALLOC_CTX *talloc_stackframe(void)
166 return talloc_stackframe_internal(0);
169 TALLOC_CTX *talloc_stackframe_pool(size_t poolsize)
171 return talloc_stackframe_internal(poolsize);
175 * Get us the current top of the talloc stack.
178 TALLOC_CTX *talloc_tos(void)
180 struct talloc_stackframe *ts =
181 (struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
183 if (ts == NULL || ts->talloc_stacksize == 0) {
184 talloc_stackframe();
185 ts = (struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
186 DEBUG(0, ("no talloc stackframe around, leaking memory\n"));
189 return ts->talloc_stack[ts->talloc_stacksize-1];
193 * return true if a talloc stackframe exists
194 * this can be used to prevent memory leaks for code that can
195 * optionally use a talloc stackframe (eg. nt_errstr())
198 bool talloc_stackframe_exists(void)
200 struct talloc_stackframe *ts =
201 (struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
203 if (ts == NULL || ts->talloc_stacksize == 0) {
204 return false;
206 return true;