Commit 08f28ff50e3f6fabcc1469fdf4a53c3a3a33eff4
2020-07-10T08:57:05
alloc: set up an allocator that fails before library init We require the library to be initialized with git_libgit2_init before it is functional. However, if a user tries to uses the library without doing so - as they might when getting started with the library for the first time - we will likely crash. This commit introduces some guard rails - now instead of having _no_ allocator by default, we'll have an allocator that always fails, and never tries to set an error message (since the thread-local state is set up by git_libgit2_init). We've modified the error retrieval function to (try to) ensure that the library has been initialized before getting the thread-local error message. (Unfortunately, we cannot determine if the thread local storage has actually been configured, this does require initialization by git_libgit2_init. But a naive attempt should be good enough for most cases.)
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diff --git a/src/alloc.c b/src/alloc.c
index 6efa104..2820d84 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -8,10 +8,22 @@
#include "alloc.h"
#include "runtime.h"
+#include "allocators/failalloc.h"
#include "allocators/stdalloc.h"
#include "allocators/win32_leakcheck.h"
-git_allocator git__allocator;
+/* Fail any allocation until git_libgit2_init is called. */
+git_allocator git__allocator = {
+ git_failalloc_malloc,
+ git_failalloc_calloc,
+ git_failalloc_strdup,
+ git_failalloc_strndup,
+ git_failalloc_substrdup,
+ git_failalloc_realloc,
+ git_failalloc_reallocarray,
+ git_failalloc_mallocarray,
+ git_failalloc_free
+};
static int setup_default_allocator(void)
{
@@ -25,10 +37,10 @@ static int setup_default_allocator(void)
int git_allocator_global_init(void)
{
/*
- * We don't want to overwrite any allocator which has been set before
- * the init function is called.
+ * We don't want to overwrite any allocator which has been set
+ * before the init function is called.
*/
- if (git__allocator.gmalloc != NULL)
+ if (git__allocator.gmalloc != git_failalloc_malloc)
return 0;
return setup_default_allocator();
diff --git a/src/allocators/failalloc.c b/src/allocators/failalloc.c
new file mode 100644
index 0000000..5257d1d
--- /dev/null
+++ b/src/allocators/failalloc.c
@@ -0,0 +1,92 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "failalloc.h"
+
+void *git_failalloc_malloc(size_t len, const char *file, int line)
+{
+ GIT_UNUSED(len);
+ GIT_UNUSED(file);
+ GIT_UNUSED(line);
+
+ return NULL;
+}
+
+void *git_failalloc_calloc(size_t nelem, size_t elsize, const char *file, int line)
+{
+ GIT_UNUSED(nelem);
+ GIT_UNUSED(elsize);
+ GIT_UNUSED(file);
+ GIT_UNUSED(line);
+
+ return NULL;
+}
+
+char *git_failalloc_strdup(const char *str, const char *file, int line)
+{
+ GIT_UNUSED(str);
+ GIT_UNUSED(file);
+ GIT_UNUSED(line);
+
+ return NULL;
+}
+
+char *git_failalloc_strndup(const char *str, size_t n, const char *file, int line)
+{
+ GIT_UNUSED(str);
+ GIT_UNUSED(n);
+ GIT_UNUSED(file);
+ GIT_UNUSED(line);
+
+ return NULL;
+}
+
+char *git_failalloc_substrdup(const char *start, size_t n, const char *file, int line)
+{
+ GIT_UNUSED(start);
+ GIT_UNUSED(n);
+ GIT_UNUSED(file);
+ GIT_UNUSED(line);
+
+ return NULL;
+}
+
+void *git_failalloc_realloc(void *ptr, size_t size, const char *file, int line)
+{
+ GIT_UNUSED(ptr);
+ GIT_UNUSED(size);
+ GIT_UNUSED(file);
+ GIT_UNUSED(line);
+
+ return NULL;
+}
+
+void *git_failalloc_reallocarray(void *ptr, size_t nelem, size_t elsize, const char *file, int line)
+{
+ GIT_UNUSED(ptr);
+ GIT_UNUSED(nelem);
+ GIT_UNUSED(elsize);
+ GIT_UNUSED(file);
+ GIT_UNUSED(line);
+
+ return NULL;
+}
+
+void *git_failalloc_mallocarray(size_t nelem, size_t elsize, const char *file, int line)
+{
+ GIT_UNUSED(nelem);
+ GIT_UNUSED(elsize);
+ GIT_UNUSED(file);
+ GIT_UNUSED(line);
+
+ return NULL;
+}
+
+void git_failalloc_free(void *ptr)
+{
+ GIT_UNUSED(ptr);
+}
diff --git a/src/allocators/failalloc.h b/src/allocators/failalloc.h
new file mode 100644
index 0000000..6115e51
--- /dev/null
+++ b/src/allocators/failalloc.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#ifndef INCLUDE_allocators_failalloc_h__
+#define INCLUDE_allocators_failalloc_h__
+
+#include "common.h"
+
+extern void *git_failalloc_malloc(size_t len, const char *file, int line);
+extern void *git_failalloc_calloc(size_t nelem, size_t elsize, const char *file, int line);
+extern char *git_failalloc_strdup(const char *str, const char *file, int line);
+extern char *git_failalloc_strndup(const char *str, size_t n, const char *file, int line);
+extern char *git_failalloc_substrdup(const char *start, size_t n, const char *file, int line);
+extern void *git_failalloc_realloc(void *ptr, size_t size, const char *file, int line);
+extern void *git_failalloc_reallocarray(void *ptr, size_t nelem, size_t elsize, const char *file, int line);
+extern void *git_failalloc_mallocarray(size_t nelem, size_t elsize, const char *file, int line);
+extern void git_failalloc_free(void *ptr);
+
+#endif
diff --git a/src/errors.c b/src/errors.c
index 5b68dd9..3d1d1c9 100644
--- a/src/errors.c
+++ b/src/errors.c
@@ -10,6 +10,7 @@
#include "threadstate.h"
#include "posix.h"
#include "buffer.h"
+#include "libgit2.h"
/********************************************
* New error handling
@@ -20,6 +21,11 @@ static git_error g_git_oom_error = {
GIT_ERROR_NOMEMORY
};
+static git_error g_git_uninitialized_error = {
+ "libgit2 has not been initialized; you must call git_libgit2_init",
+ GIT_ERROR_INVALID
+};
+
static void set_error_from_buffer(int error_class)
{
git_error *error = &GIT_THREADSTATE->error_t;
@@ -131,6 +137,10 @@ void git_error_clear(void)
const git_error *git_error_last(void)
{
+ /* If the library is not initialized, return a static error. */
+ if (!git_libgit2_init_count())
+ return &g_git_uninitialized_error;
+
return GIT_THREADSTATE->last_error;
}