livepatch: Cleanup module page permission changes

Calling set_memory_rw() and set_memory_ro() for every iteration of the
loop in klp_write_object_relocations() is messy, inefficient, and
error-prone.

Change all the read-only pages to read-write before the loop and convert
them back to read-only again afterwards.

Suggested-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/arch/x86/kernel/livepatch.c b/arch/x86/kernel/livepatch.c
index bcc06e82a593e3b843dc3b27de1fe7e3f3ef250d..92fc1a51f994ef924ab33c87e9f52ed654e06ab5 100644 (file)
--- a/arch/x86/kernel/livepatch.c
+++ b/arch/x86/kernel/livepatch.c
@@ -20,8 +20,6 @@
 
 #include <linux/module.h>
 #include <linux/uaccess.h>
-#include <asm/cacheflush.h>
-#include <asm/page_types.h>
 #include <asm/elf.h>
 #include <asm/livepatch.h>
 
@@ -38,8 +36,7 @@
 int klp_write_module_reloc(struct module *mod, unsigned long type,
                           unsigned long loc, unsigned long value)
 {
-       int ret, numpages, size = 4;
-       bool readonly;
+       size_t size = 4;
        unsigned long val;
        unsigned long core = (unsigned long)mod->core_layout.base;
        unsigned long core_size = mod->core_layout.size;
@@ -69,23 +66,5 @@ int klp_write_module_reloc(struct module *mod, unsigned long type,
                /* loc does not point to any symbol inside the module */
                return -EINVAL;
 
-       readonly = false;
-
-#ifdef CONFIG_DEBUG_SET_MODULE_RONX
-       if (loc < core + mod->core_layout.ro_size)
-               readonly = true;
-#endif
-
-       /* determine if the relocation spans a page boundary */
-       numpages = ((loc & PAGE_MASK) == ((loc + size) & PAGE_MASK)) ? 1 : 2;
-
-       if (readonly)
-               set_memory_rw(loc & PAGE_MASK, numpages);
-
-       ret = probe_kernel_write((void *)loc, &val, size);
-
-       if (readonly)
-               set_memory_ro(loc & PAGE_MASK, numpages);
-
-       return ret;
+       return probe_kernel_write((void *)loc, &val, size);
 }

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 94893e844e445c18d1ac51db328217ff888511df..bc2c85c064c1b73cf2c393dc2278e3e3bc6dc7af 100644 (file)
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -28,6 +28,7 @@
 #include <linux/list.h>
 #include <linux/kallsyms.h>
 #include <linux/livepatch.h>
+#include <asm/cacheflush.h>
 
 /**
  * struct klp_ops - structure for tracking registered ftrace ops structs
@@ -232,7 +233,7 @@ static int klp_find_external_symbol(struct module *pmod, const char *name,
 static int klp_write_object_relocations(struct module *pmod,
                                        struct klp_object *obj)
 {
-       int ret;
+       int ret = 0;
        unsigned long val;
        struct klp_reloc *reloc;
 
@@ -242,13 +243,16 @@ static int klp_write_object_relocations(struct module *pmod,
        if (WARN_ON(!obj->relocs))
                return -EINVAL;
 
+       module_disable_ro(pmod);
+
        for (reloc = obj->relocs; reloc->name; reloc++) {
                /* discover the address of the referenced symbol */
                if (reloc->external) {
                        if (reloc->sympos > 0) {
                                pr_err("non-zero sympos for external reloc symbol '%s' is not supported\n",
                                       reloc->name);
-                               return -EINVAL;
+                               ret = -EINVAL;
+                               goto out;
                        }
                        ret = klp_find_external_symbol(pmod, reloc->name, &val);
                } else
@@ -257,18 +261,20 @@ static int klp_write_object_relocations(struct module *pmod,
                                                     reloc->sympos,
                                                     &val);
                if (ret)
-                       return ret;
+                       goto out;
 
                ret = klp_write_module_reloc(pmod, reloc->type, reloc->loc,
                                             val + reloc->addend);
                if (ret) {
                        pr_err("relocation failed for symbol '%s' at 0x%016lx (%d)\n",
                               reloc->name, val, ret);
-                       return ret;
+                       goto out;
                }
        }
 
-       return 0;
+out:
+       module_enable_ro(pmod);
+       return ret;
 }
 
 static void notrace klp_ftrace_handler(unsigned long ip,