[RFC 12/12] module: use aliases to find module on find_module_all()

From: Luis Chamberlain <mcgrof@kernel.org>
To: linux-modules@vger.kernel.org, linux-kernel@vger.kernel.org,
	pmladek@suse.com, david@redhat.com, petr.pavlu@suse.com,
	prarit@redhat.com
Cc: christophe.leroy@csgroup.eu, song@kernel.org, mcgrof@kernel.org,
	torvalds@linux-foundation.org
Subject: [RFC 12/12] module: use aliases to find module on find_module_all()
Date: Fri, 10 Mar 2023 21:17:12 -0800	[thread overview]
Message-ID: <20230311051712.4095040-13-mcgrof@kernel.org> (raw)
In-Reply-To: <20230311051712.4095040-1-mcgrof@kernel.org>

Modules can have a series of aliases, but we don't currently use
them to check if a module is already loaded. Part of this is because
load_module() will stick to checking for already loaded modules using
the actual module name, not an alias. Its however desriable to also
check for aliases on find_module_all() for existing callers and future
callers. The curent gain to using aliases on find_module_all() will
simply be to be able to support unloading modules using the alias using
the delete_module() syscall.

You can debug this with dynamic debug:

GRUB_CMDLINE_LINUX_DEFAULT="dyndbg=\"func module_process_aliases +p; func module_name_match +p; \" "

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
 kernel/module/aliases.c  | 17 +++++++++++++++++
 kernel/module/internal.h |  5 +++++
 kernel/module/main.c     | 24 +++++++++++++++++++++++-
 3 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/kernel/module/aliases.c b/kernel/module/aliases.c
index 2f30c9d4c765..69518bc5169a 100644
--- a/kernel/module/aliases.c
+++ b/kernel/module/aliases.c
@@ -90,3 +90,20 @@ int module_process_aliases(struct module *mod, struct load_info *info)
 
 	return -ENOMEM;
 }
+
+bool module_name_match_aliases(struct module *mod, const char *name, size_t len)
+{
+	unsigned int i;
+	const char *alias;
+
+	for (i=0; i < mod->num_aliases; i++) {
+		alias = mod->aliases[i];
+		if (strlen(alias) == len && !memcmp(alias, name, len)) {
+			pr_debug("module %s alias matched: alias[%u] = %s\n",
+				 mod->name, i, alias);
+			return true;
+		}
+	}
+
+	return false;
+}
diff --git a/kernel/module/internal.h b/kernel/module/internal.h
index 40bb80ed21e2..78aaad74f4ca 100644
--- a/kernel/module/internal.h
+++ b/kernel/module/internal.h
@@ -306,6 +306,7 @@ static inline int same_magic(const char *amagic, const char *bmagic, bool has_cr
 #ifdef CONFIG_MODULE_KERNEL_ALIAS
 void free_mod_aliases(struct module *mod);
 int module_process_aliases(struct module *mod, struct load_info *info);
+bool module_name_match_aliases(struct module *mod, const char *name, size_t len);
 #else
 static void free_mod_aliases(struct module *mod)
 {
@@ -314,4 +315,8 @@ static int module_process_aliases(struct module *mod, struct load_info *info)
 {
 	return 0;
 }
+static bool module_name_match_aliases(struct module *mod, const char *name, size_t len)
+{
+	return false;
+}
 #endif /* CONFIG_MODULE_KERNEL_ALIAS */
diff --git a/kernel/module/main.c b/kernel/module/main.c
index bc9202b60d55..cf044329da3c 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -338,6 +338,28 @@ bool find_symbol(struct find_symbol_arg *fsa)
 	return false;
 }
 
+static bool module_name_match(struct module *mod, const char *name, size_t len)
+{
+	unsigned int i;
+	const char *alias;
+
+	if (strlen(mod->name) == len && !memcmp(mod->name, name, len))
+		return true;
+
+	return module_name_match_aliases(mod, name, len);
+
+	for (i=0; i < mod->num_aliases; i++) {
+		alias = mod->aliases[i];
+		if (strlen(alias) == len && !memcmp(alias, name, len)) {
+			pr_debug("module %s alias matched: alias[%u] = %s\n",
+				 mod->name, i, alias);
+			return true;
+		}
+	}
+
+	return false;
+}
+
 /*
  * Search for module by name: must hold module_mutex (or preempt disabled
  * for read-only access).
@@ -353,7 +375,7 @@ struct module *find_module_all(const char *name, size_t len,
 				lockdep_is_held(&module_mutex)) {
 		if (!even_unformed && mod->state == MODULE_STATE_UNFORMED)
 			continue;
-		if (strlen(mod->name) == len && !memcmp(mod->name, name, len))
+		if (module_name_match(mod, name, len))
 			return mod;
 	}
 	return NULL;
-- 
2.39.1

