lib: prevent module unloading if memory is not freed

Skip freeing module's data section if there are non-zero allocation tags
because otherwise, once these allocations are freed, the access to their
code tag would cause UAF.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Suren Baghdasaryan <[email protected]>
Tested-by: Kees Cook <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Alex Gaynor <[email protected]>
Cc: Alice Ryhl <[email protected]>
Cc: Andreas Hindborg <[email protected]>
Cc: Benno Lossin <[email protected]>
Cc: "Björn Roy Baron" <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Dennis Zhou <[email protected]>
Cc: Gary Guo <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: Miguel Ojeda <[email protected]>
Cc: Pasha Tatashin <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Wedson Almeida Filho <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

1 files changed, 19 insertions, 8 deletions

diff --git a/kernel/module/main.c b/kernel/module/main.c
index ffa6b3e9cb43..2d25eebc549d 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -1211,15 +1211,19 @@ static void *module_memory_alloc(unsigned int size, enum mod_mem_type type)
 	return module_alloc(size);
 }
 
-static void module_memory_free(void *ptr, enum mod_mem_type type)
+static void module_memory_free(void *ptr, enum mod_mem_type type,
+			       bool unload_codetags)
 {
+	if (!unload_codetags && mod_mem_type_is_core_data(type))
+		return;
+
 	if (mod_mem_use_vmalloc(type))
 		vfree(ptr);
 	else
 		module_memfree(ptr);
 }
 
-static void free_mod_mem(struct module *mod)
+static void free_mod_mem(struct module *mod, bool unload_codetags)
 {
 	for_each_mod_mem_type(type) {
 		struct module_memory *mod_mem = &mod->mem[type];
@@ -1230,20 +1234,27 @@ static void free_mod_mem(struct module *mod)
 		/* Free lock-classes; relies on the preceding sync_rcu(). */
 		lockdep_free_key_range(mod_mem->base, mod_mem->size);
 		if (mod_mem->size)
-			module_memory_free(mod_mem->base, type);
+			module_memory_free(mod_mem->base, type,
+					   unload_codetags);
 	}
 
 	/* MOD_DATA hosts mod, so free it at last */
 	lockdep_free_key_range(mod->mem[MOD_DATA].base, mod->mem[MOD_DATA].size);
-	module_memory_free(mod->mem[MOD_DATA].base, MOD_DATA);
+	module_memory_free(mod->mem[MOD_DATA].base, MOD_DATA, unload_codetags);
 }
 
 /* Free a module, remove from lists, etc. */
 static void free_module(struct module *mod)
 {
+	bool unload_codetags;
+
 	trace_module_free(mod);
 
-	codetag_unload_module(mod);
+	unload_codetags = codetag_unload_module(mod);
+	if (!unload_codetags)
+		pr_warn("%s: memory allocation(s) from the module still alive, cannot unload cleanly\n",
+			mod->name);
+
 	mod_sysfs_teardown(mod);
 
 	/*
@@ -1285,7 +1296,7 @@ static void free_module(struct module *mod)
 	kfree(mod->args);
 	percpu_modfree(mod);
 
-	free_mod_mem(mod);
+	free_mod_mem(mod, unload_codetags);
 }
 
 void *__symbol_get(const char *symbol)
@@ -2298,7 +2309,7 @@ static int move_module(struct module *mod, struct load_info *info)
 	return 0;
 out_enomem:
 	for (t--; t >= 0; t--)
-		module_memory_free(mod->mem[t].base, t);
+		module_memory_free(mod->mem[t].base, t, true);
 	return ret;
 }
 
@@ -2428,7 +2439,7 @@ static void module_deallocate(struct module *mod, struct load_info *info)
 	percpu_modfree(mod);
 	module_arch_freeing_init(mod);
 
-	free_mod_mem(mod);
+	free_mod_mem(mod, true);
 }
 
 int __weak module_finalize(const Elf_Ehdr *hdr,