diff mbox series

[v4,13/36] lib: prevent module unloading if memory is not freed

Message ID 20240221194052.927623-14-surenb@google.com
State New
Headers
Series Memory allocation profiling |

Commit Message

Suren Baghdasaryan Feb. 21, 2024, 7:40 p.m. UTC 
  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.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
 include/linux/codetag.h |  6 +++---
 kernel/module/main.c    | 23 +++++++++++++++--------
 lib/codetag.c           | 11 ++++++++---
 3 files changed, 26 insertions(+), 14 deletions(-)

Comments

Vlastimil Babka Feb. 26, 2024, 4:58 p.m. UTC | #1 
On 2/21/24 20:40, Suren Baghdasaryan wrote:
> 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.
> 
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>

I know that module unloading was never considered really supported etc.
But should we printk something so the admin knows why it didn't unload, and
can go check those outstanding allocations?
Suren Baghdasaryan Feb. 26, 2024, 5:13 p.m. UTC | #2 
On Mon, Feb 26, 2024 at 8:58 AM Vlastimil Babka <vbabka@suse.cz> wrote:
>
> On 2/21/24 20:40, Suren Baghdasaryan wrote:
> > 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.
> >
> > Signed-off-by: Suren Baghdasaryan <surenb@google.com>
>
> I know that module unloading was never considered really supported etc.
> But should we printk something so the admin knows why it didn't unload, and
> can go check those outstanding allocations?

Yes, that sounds reasonable. I'll add a pr_warn() in the next version.
Thanks!

>
> --
> To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com.
>
diff mbox series

Patch

diff --git a/include/linux/codetag.h b/include/linux/codetag.h
index c44f5b83f24d..bfd0ba5c4185 100644
--- 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 f400ba076cc7..658b631e76ad 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 +1234,23 @@  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);
 	mod_sysfs_teardown(mod);
 
 	/*
@@ -1285,7 +1292,7 @@  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 +2305,7 @@  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 +2435,7 @@  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 9af22648dbfa..b13412ca57cc 100644
--- 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;
@@ -239,12 +240,13 @@  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) {
@@ -261,7 +263,8 @@  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);
@@ -270,4 +273,6 @@  void codetag_unload_module(struct module *mod)
 		up_write(&cttype->mod_lock);
 	}
 	mutex_unlock(&codetag_lock);
+
+	return unload_ok;
 }