livepatch: add module locking around kallsyms calls

The list of loaded modules is walked through in
module_kallsyms_on_each_symbol (called by kallsyms_on_each_symbol). The
module_mutex lock should be acquired to prevent potential corruptions
in the list.

This was uncovered with new lockdep asserts in module code introduced by
the commit 0be964be0d45 ("module: Sanitize RCU usage and locking") in
recent next- trees.

Signed-off-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 13 insertions, 5 deletions

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 284e2691e380..9ec555732f1a 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -179,7 +179,9 @@ static int klp_find_object_symbol(const char *objname, const char *name,
                 .count = 0
         };
 
+        mutex_lock(&module_mutex);
         kallsyms_on_each_symbol(klp_find_callback, &args);
+        mutex_unlock(&module_mutex);
 
         if (args.count == 0)
                 pr_err("symbol '%s' not found in symbol table\n", name);
@@ -219,13 +221,19 @@ static int klp_verify_vmlinux_symbol(const char *name, unsigned long addr)
                 .name = name,
                 .addr = addr,
         };
+        int ret;
 
-        if (kallsyms_on_each_symbol(klp_verify_callback, &args))
-                return 0;
+        mutex_lock(&module_mutex);
+        ret = kallsyms_on_each_symbol(klp_verify_callback, &args);
+        mutex_unlock(&module_mutex);
 
-        pr_err("symbol '%s' not found at specified address 0x%016lx, kernel mismatch?\n",
-                name, addr);
-        return -EINVAL;
+        if (!ret) {
+                pr_err("symbol '%s' not found at specified address 0x%016lx, kernel mismatch?\n",
+                        name, addr);
+                return -EINVAL;
+        }
+
+        return 0;
 }
 
 static int klp_find_verify_func_addr(struct klp_object *obj,