When checking to see if a shared object is already loaded, look for

a device/inode match if no pathname match is found.

libexec/rtld-elf/map_object.c

@@ -27,6 +27,7 @@
 
 #include <sys/param.h>
 #include <sys/mman.h>
+#include <sys/stat.h>
 
 #include <errno.h>
 #include <stddef.h>
@@ -47,7 +48,7 @@ static int protflags(int);	/* Elf flags -> mmap protection */
  * for the shared object.  Returns NULL on failure.
  */
 Obj_Entry *
-map_object(int fd, const char *path)
+map_object(int fd, const char *path, const struct stat *sb)
 {
     Obj_Entry *obj;
     union {
@@ -228,6 +229,10 @@ map_object(int fd, const char *path)
     }
 
     obj = obj_new();
+    if (sb != NULL) {
+	obj->dev = sb->st_dev;
+	obj->ino = sb->st_ino;
+    }
     obj->mapbase = mapbase;
     obj->mapsize = mapsize;
     obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) -

libexec/rtld-elf/rtld.c

@@ -37,6 +37,7 @@
 
 #include <sys/param.h>
 #include <sys/mman.h>
+#include <sys/stat.h>
 
 #include <dlfcn.h>
 #include <err.h>
@@ -244,7 +245,7 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
     if (aux_info[AT_EXECFD] != NULL) {	/* Load the main program. */
 	int fd = aux_info[AT_EXECFD]->a_un.a_val;
 	dbg("loading main program");
-	obj_main = map_object(fd, argv0);
+	obj_main = map_object(fd, argv0, NULL);
 	close(fd);
 	if (obj_main == NULL)
 	    die();
@@ -983,20 +984,42 @@ static Obj_Entry *
 load_object(char *path)
 {
     Obj_Entry *obj;
+    int fd = -1;
+    struct stat sb;
 
     for (obj = obj_list->next;  obj != NULL;  obj = obj->next)
 	if (strcmp(obj->path, path) == 0)
 	    break;
 
-    if (obj == NULL) {	/* First use of this object, so we must map it in */
-	int fd;
-
+    /*
+     * If we didn't find a match by pathname, open the file and check
+     * again by device and inode.  This avoids false mismatches caused
+     * by multiple links or ".." in pathnames.
+     *
+     * To avoid a race, we open the file and use fstat() rather than
+     * using stat().
+     */
+    if (obj == NULL) {
 	if ((fd = open(path, O_RDONLY)) == -1) {
 	    _rtld_error("Cannot open \"%s\"", path);
 	    return NULL;
 	}
+	if (fstat(fd, &sb) == -1) {
+	    _rtld_error("Cannot fstat \"%s\"", path);
+	    close(fd);
+	    return NULL;
+	}
+	for (obj = obj_list->next;  obj != NULL;  obj = obj->next) {
+	    if (obj->ino == sb.st_ino && obj->dev == sb.st_dev) {
+		close(fd);
+		break;
+	    }
+	}
+    }
+
+    if (obj == NULL) {	/* First use of this object, so we must map it in */
 	dbg("loading \"%s\"", path);
-	obj = map_object(fd, path);
+	obj = map_object(fd, path, &sb);
 	close(fd);
 	if (obj == NULL) {
 	    free(path);

libexec/rtld-elf/rtld.h

@@ -49,6 +49,7 @@ typedef unsigned char bool;
 #define false	0
 #define true	1
 
+struct stat;
 struct Struct_Obj_Entry;
 
 typedef struct Struct_Objlist_Entry {
@@ -82,6 +83,8 @@ typedef struct Struct_Obj_Entry {
     Objlist dldags;		/* Object belongs to these dlopened DAGs (%) */
     Objlist dagmembers;		/* DAG has these members (%) */
     char *path;			/* Pathname of underlying file (%) */
+    dev_t dev;			/* Object's filesystem's device */
+    ino_t ino;			/* Object's inode number */
     unsigned long mark;		/* Set to "curmark" to avoid repeat visits */
     int refcount;
     int dl_refcount;		/* Number of times loaded by dlopen */
@@ -135,7 +138,7 @@ typedef struct Struct_Obj_Entry {
 #define RTLD_VERSION	1
 
 extern void _rtld_error(const char *, ...) __printflike(1, 2);
-extern Obj_Entry *map_object(int, const char *);
+extern Obj_Entry *map_object(int, const char *, const struct stat *);
 extern void *xcalloc(size_t);
 extern void *xmalloc(size_t);
 extern char *xstrdup(const char *);