[patch] minimal-malloc.patch

minimal-malloc.patch (text/plain), 5.07 KB, created by Ed Catmur on 2007-10-21 21:59:36 UTC

--- src/Makefile.am	2007/03/19 22:15:22	1.1
+++ src/Makefile.am	2007/03/19 22:28:33
@@ -24,6 +24,7 @@ libsandbox_la_SOURCES = \
 	libsandbox.c      \
 	canonicalize.c    \
 	sandbox_utils.c   \
+	mmalloc.c         \
 	$(LOCAL_INCLUDES)
 
 sandbox_CFLAGS = -DOUTSIDE_LIBSANDBOX
--- src/mmalloc.c	2007/10/06 23:20:26	1.1
+++ src/mmalloc.c	2007/10/06 23:44:54
@@ -0,0 +1,147 @@
+/* Minimal mmap-based malloc/free implementation to be used by libsandbox
+ * internal routines, since we can't trust the current process to have a
+ * malloc/free implementation that is sane and available at all times.
+ */
+
+#include <stdlib.h>   /* malloc()/free() prototypes */
+#include <string.h>   /* mem*(), strdup() prototype */
+
+#include <sys/mman.h> /* mmap() */
+#include <errno.h>
+#include <limits.h>
+
+#include "sandbox.h"
+
+static int checked_env = 0;
+static int env_sandbox_local_malloc = 0;
+
+#define check_dlsym(_name) \
+{ \
+	int old_errno = errno; \
+	if (!true_ ## _name) \
+		true_ ## _name = get_dlsym(#_name, NULL); \
+	errno = old_errno; \
+}
+
+#define SB_MALLOC_TO_MMAP(ptr) ((void*)(((size_t*)ptr) - 1))
+#define SB_MMAP_TO_MALLOC(ptr) ((void*)(((size_t*)ptr) + 1))
+#define SB_MALLOC_TO_SIZE(ptr) (*((size_t*)SB_MALLOC_TO_MMAP(ptr)))
+
+static void *(*true_malloc)(size_t size) = NULL;
+void *malloc(size_t size)
+{
+	if (!checked_env) {
+		env_sandbox_local_malloc = (getenv(ENV_SANDBOX_LOCAL_MALLOC) != NULL);
+		checked_env = 1;
+	}
+	if (!env_sandbox_local_malloc) {
+		check_dlsym(malloc);
+		return true_malloc(size);
+	} else {
+		size_t *ret;
+		size += sizeof(size_t);
+		ret = mmap(0, size, PROT_READ|PROT_WRITE,
+				MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+		if (ret == MAP_FAILED)
+			return NULL;
+		*ret = size;
+		return SB_MMAP_TO_MALLOC(ret);
+	}
+}
+
+static void (*true_free)(void *ptr) = NULL;
+void free(void *ptr)
+{
+	if (!checked_env) {
+		env_sandbox_local_malloc = (getenv(ENV_SANDBOX_LOCAL_MALLOC) != NULL);
+		checked_env = 1;
+	}
+	if (!env_sandbox_local_malloc) {
+		check_dlsym(free);
+		true_free(ptr);
+	} else {
+		if (ptr == NULL)
+			return;
+		munmap(SB_MALLOC_TO_MMAP(ptr), SB_MALLOC_TO_SIZE(ptr));
+	}
+}
+
+static void *(*true_calloc)(size_t nmemb, size_t size) = NULL;
+void *calloc(size_t nmemb, size_t size)
+{
+	if (!checked_env) {
+		env_sandbox_local_malloc = (getenv(ENV_SANDBOX_LOCAL_MALLOC) != NULL);
+		checked_env = 1;
+	}
+	if (!env_sandbox_local_malloc) {
+		check_dlsym(calloc);
+		return true_calloc(nmemb, size);
+	} else {
+		void *ret;
+		size_t malloc_size = nmemb * size;
+		ret = malloc(malloc_size); /* dont care about overflow */
+		if (ret == NULL)
+			return NULL;
+		memset(ret, 0x00, malloc_size);
+		return ret;
+	}
+}
+
+static void *(*true_realloc)(void *ptr, size_t size) = NULL;
+void *realloc(void *ptr, size_t size)
+{
+	if (!checked_env) {
+		env_sandbox_local_malloc = (getenv(ENV_SANDBOX_LOCAL_MALLOC) != NULL);
+		checked_env = 1;
+	}
+	if (!env_sandbox_local_malloc) {
+		check_dlsym(realloc);
+		return true_realloc(ptr, size);
+	} else {
+		void *ret;
+		size_t old_malloc_size;
+
+		if (ptr == NULL)
+			return malloc(size);
+		if (size == 0) {
+			free(ptr);
+			return ptr;
+		}
+
+		old_malloc_size = SB_MALLOC_TO_SIZE(ptr);
+		ret = malloc(size);
+		if (ret == NULL)
+			return NULL;
+		memcpy(ret, ptr, (size < old_malloc_size ? size
+					: old_malloc_size));
+		free(ptr);
+		return ret;
+	}
+}
+
+static char *(*true_strdup)(const char *s) = NULL;
+#ifdef strdup
+#undef strdup
+#endif
+char *strdup(const char *s)
+{
+	if (!checked_env) {
+		env_sandbox_local_malloc = (getenv(ENV_SANDBOX_LOCAL_MALLOC) != NULL);
+		checked_env = 1;
+	}
+	if (!env_sandbox_local_malloc) {
+		check_dlsym(strdup);
+		return true_strdup(s);
+	} else {
+		size_t len;
+		char *ret;
+
+		if (s == NULL)
+			return NULL;
+		len = strlen(s);
+		ret = malloc(len + 1);
+		if (ret == NULL)
+			return NULL;
+		return memcpy(ret, s, len + 1);
+	}
+}
--- src/sandbox.h	2007/10/06 23:19:48	1.1
+++ src/sandbox.h	2007/10/06 23:38:25
@@ -52,6 +52,8 @@
 #define ENV_SANDBOX_ACTIVE     "SANDBOX_ACTIVE"
 #define SANDBOX_ACTIVE         "armedandready"
 
+#define ENV_SANDBOX_LOCAL_MALLOC "SANDBOX_LOCAL_MALLOC"
+
 #define DEFAULT_BEEP_COUNT     3
 
 #define SB_BUF_LEN             2048
@@ -110,6 +110,7 @@ char *gbasename (const char *path);
 char *erealpath(const char *, char *);
 #ifndef OUTSIDE_LIBSANDBOX
 char *egetcwd(char *, size_t);
+void *get_dlsym(const char *, const char *);
 #endif
 
 #endif /* __SANDBOX_H__ */
--- src/libsandbox.c	2007/10/06 23:19:48	1.1
+++ src/libsandbox.c	2007/10/06 23:30:29
@@ -121,7 +121,6 @@ static int sb_path_size_warning = 0;
 void __attribute__ ((constructor)) libsb_init(void);
 void __attribute__ ((destructor)) libsb_fini(void);
 
-static void *get_dlsym(const char *, const char *);
 static int canonicalize(const char *, char *);
 static char *resolve_path(const char *, int);
 static int check_prefixes(char **, int, const char *);
@@ -185,7 +184,7 @@ void __attribute__ ((constructor)) libsb
 	errno = old_errno;
 }
 
-static void *get_dlsym(const char *symname, const char *symver)
+void *get_dlsym(const char *symname, const char *symver)
 {
 	void *symaddr = NULL;