diff options
Diffstat (limited to 'elf/dl-lookup.c')
| -rw-r--r-- | elf/dl-lookup.c | 83 |
1 files changed, 60 insertions, 23 deletions
diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c index f4e5ce8..ce28f86 100644 --- a/elf/dl-lookup.c +++ b/elf/dl-lookup.c @@ -86,36 +86,42 @@ dl_new_hash (const char *s) /* Add extra dependency on MAP to UNDEF_MAP. */ static int internal_function -add_dependency (struct link_map *undef_map, struct link_map *map) +add_dependency (struct link_map *undef_map, struct link_map *map, int flags) { struct link_map **list; struct link_map *runp; unsigned int act; unsigned int i; int result = 0; + unsigned long long int serial; /* Avoid self-references and references to objects which cannot be unloaded anyway. */ if (undef_map == map) return 0; - /* Make sure nobody can unload the object while we are at it. */ - __rtld_lock_lock_recursive (GL(dl_load_lock)); - - /* Avoid references to objects which cannot be unloaded anyway. */ - if (map->l_type != lt_loaded - || (map->l_flags_1 & DF_1_NODELETE) != 0) - goto out; + /* Save serial number of the target MAP. */ + serial = map->l_serial; - /* If the object with the undefined reference cannot be removed ever - just make sure the same is true for the object which contains the - definition. */ - if (undef_map->l_type != lt_loaded - || (undef_map->l_flags_1 & DF_1_NODELETE) != 0) + /* Make sure nobody can unload the object while we are at it. */ + if (__builtin_expect (flags & DL_LOOKUP_GSCOPE_LOCK, 0)) { - map->l_flags_1 |= DF_1_NODELETE; - goto out; + /* We can't just call __rtld_lock_lock_recursive (GL(dl_load_lock)) + here, that can result in ABBA deadlock. */ + THREAD_GSCOPE_RESET_FLAG (); + __rtld_lock_lock_recursive (GL(dl_load_lock)); + THREAD_GSCOPE_SET_FLAG (); + /* While MAP value won't change, after THREAD_GSCOPE_RESET_FLAG () + it can e.g. point to unallocated memory. So avoid the optimizer + treating the above read from MAP->l_serial as ensurance it + can safely dereference it. */ + map = atomic_forced_read (map); } + else + __rtld_lock_lock_recursive (GL(dl_load_lock)); + + /* From this point on it is unsafe to dereference MAP, until it + has been found in one of the lists. */ /* Determine whether UNDEF_MAP already has a reference to MAP. First look in the normal dependencies. */ @@ -125,7 +131,7 @@ add_dependency (struct link_map *undef_map, struct link_map *map) for (i = 0; list[i] != NULL; ++i) if (list[i] == map) - goto out; + goto out_check; } /* No normal dependency. See whether we already had to add it @@ -135,7 +141,7 @@ add_dependency (struct link_map *undef_map, struct link_map *map) for (i = 0; i < act; ++i) if (list[i] == map) - goto out; + goto out_check; /* The object is not yet in the dependency list. Before we add it make sure just one more time the object we are about to @@ -148,7 +154,29 @@ add_dependency (struct link_map *undef_map, struct link_map *map) if (runp != NULL) { - /* The object is still available. Add the reference now. */ + /* The object is still available. */ + + /* MAP could have been dlclosed, freed and then some other dlopened + library could have the same link_map pointer. */ + if (map->l_serial != serial) + goto out_check; + + /* Avoid references to objects which cannot be unloaded anyway. */ + if (map->l_type != lt_loaded + || (map->l_flags_1 & DF_1_NODELETE) != 0) + goto out; + + /* If the object with the undefined reference cannot be removed ever + just make sure the same is true for the object which contains the + definition. */ + if (undef_map->l_type != lt_loaded + || (undef_map->l_flags_1 & DF_1_NODELETE) != 0) + { + map->l_flags_1 |= DF_1_NODELETE; + goto out; + } + + /* Add the reference now. */ if (__builtin_expect (act >= undef_map->l_reldepsmax, 0)) { /* Allocate more memory for the dependency list. Since this @@ -196,6 +224,11 @@ add_dependency (struct link_map *undef_map, struct link_map *map) __rtld_lock_unlock_recursive (GL(dl_load_lock)); return result; + + out_check: + if (map->l_serial != serial) + result = -1; + goto out; } static void @@ -227,9 +260,11 @@ _dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map, bump_num_relocations (); - /* No other flag than DL_LOOKUP_ADD_DEPENDENCY is allowed if we look - up a versioned symbol. */ - assert (version == NULL || (flags & ~(DL_LOOKUP_ADD_DEPENDENCY)) == 0); + /* No other flag than DL_LOOKUP_ADD_DEPENDENCY or DL_LOOKUP_GSCOPE_LOCK + is allowed if we look up a versioned symbol. */ + assert (version == NULL + || (flags & ~(DL_LOOKUP_ADD_DEPENDENCY | DL_LOOKUP_GSCOPE_LOCK)) + == 0); size_t i = 0; if (__builtin_expect (skip_map != NULL, 0)) @@ -335,10 +370,12 @@ _dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map, runtime lookups. */ && (flags & DL_LOOKUP_ADD_DEPENDENCY) != 0 /* Add UNDEF_MAP to the dependencies. */ - && add_dependency (undef_map, current_value.m) < 0) + && add_dependency (undef_map, current_value.m, flags) < 0) /* Something went wrong. Perhaps the object we tried to reference was just removed. Try finding another definition. */ - return _dl_lookup_symbol_x (undef_name, undef_map, ref, symbol_scope, + return _dl_lookup_symbol_x (undef_name, undef_map, ref, + (flags & DL_LOOKUP_GSCOPE_LOCK) + ? undef_map->l_scope : symbol_scope, version, type_class, flags, skip_map); /* The object is used. */ |