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/20240321163705.3067592-13-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Tested-by: Kees Cook <keescook@chromium.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alex Gaynor <alex.gaynor@gmail.com>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Andreas Hindborg <a.hindborg@samsung.com>
Cc: Benno Lossin <benno.lossin@proton.me>
Cc: "Björn Roy Baron" <bjorn3_gh@protonmail.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Gary Guo <gary@garyguo.net>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wedson Almeida Filho <wedsonaf@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/codetag.h b/include/linux/codetag.h
index c44f5b83f24d6a2cc690a19106f530e9caf169a6..bfd0ba5c4185c28e99fc6a9139fd55d1bbface4c 100644 (file)
--- a/include/linux/codetag.h
+++ b/include/linux/codetag.h
@@ -35,7 +35,7 @@ struct codetag_type_desc {
        size_t tag_size;
        void (*module_load)(struct codetag_type *cttype,
                            struct codetag_module *cmod);
-       void (*module_unload)(struct codetag_type *cttype,
+       bool (*module_unload)(struct codetag_type *cttype,
                              struct codetag_module *cmod);
 };
 
@@ -71,10 +71,10 @@ codetag_register_type(const struct codetag_type_desc *desc);
 
 #if defined(CONFIG_CODE_TAGGING) && defined(CONFIG_MODULES)
 void codetag_load_module(struct module *mod);
-void codetag_unload_module(struct module *mod);
+bool codetag_unload_module(struct module *mod);
 #else
 static inline void codetag_load_module(struct module *mod) {}
-static inline void codetag_unload_module(struct module *mod) {}
+static inline bool codetag_unload_module(struct module *mod) { return true; }
 #endif
 
 #endif /* _LINUX_CODETAG_H */

diff --git a/kernel/module/main.c b/kernel/module/main.c
index ffa6b3e9cb43bccf5107ce56d5fa15fd98f4aa5d..2d25eebc549dbee1934c45b2a91a38895c316b4a 100644 (file)
--- 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,

diff --git a/lib/codetag.c b/lib/codetag.c
index 54d2828eba25667bf89636c94f31095f149a1833..408062f722ced08994f354f1d7eac68da3c38711 100644 (file)
--- a/lib/codetag.c
+++ b/lib/codetag.c
@@ -5,6 +5,7 @@
 #include <linux/module.h>
 #include <linux/seq_buf.h>
 #include <linux/slab.h>
+#include <linux/vmalloc.h>
 
 struct codetag_type {
        struct list_head link;
@@ -206,12 +207,13 @@ void codetag_load_module(struct module *mod)
        mutex_unlock(&codetag_lock);
 }
 
-void codetag_unload_module(struct module *mod)
+bool codetag_unload_module(struct module *mod)
 {
        struct codetag_type *cttype;
+       bool unload_ok = true;
 
        if (!mod)
-               return;
+               return true;
 
        mutex_lock(&codetag_lock);
        list_for_each_entry(cttype, &codetag_types, link) {
@@ -228,7 +230,8 @@ void codetag_unload_module(struct module *mod)
                }
                if (found) {
                        if (cttype->desc.module_unload)
-                               cttype->desc.module_unload(cttype, cmod);
+                               if (!cttype->desc.module_unload(cttype, cmod))
+                                       unload_ok = false;
 
                        cttype->count -= range_size(cttype, &cmod->range);
                        idr_remove(&cttype->mod_idr, mod_id);
@@ -237,6 +240,8 @@ void codetag_unload_module(struct module *mod)
                up_write(&cttype->mod_lock);
        }
        mutex_unlock(&codetag_lock);
+
+       return unload_ok;
 }
 
 #else /* CONFIG_MODULES */