diff mbox series

[1/5] jump_label,module: Don't alloc static_key_mod for __ro_after_init keys

Message ID 20231120105528.760306-2-vschneid@redhat.com (mailing list archive)
State New, archived
Headers show
Series jump_label: Fix __ro_after_init keys for modules & annotate some keys | expand

Commit Message

Valentin Schneider Nov. 20, 2023, 10:55 a.m. UTC 
From: Peter Zijlstra <peterz@infradead.org>

When a static_key is marked ro_after_init, its state will never change
(after init), therefore jump_label_update() will never need to iterate
the entries, and thus module load won't actually need to track this --
avoiding the static_key::next write.

Therefore, mark these keys such that jump_label_add_module() might
recognise them and avoid the modification.

Use the special state: 'static_key_linked(key) && !static_key_mod(key)'
to denote such keys.

Link: http://lore.kernel.org/r/20230705204142.GB2813335@hirez.programming.kicks-ass.net
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
---
 include/asm-generic/sections.h |  5 ++++
 include/linux/jump_label.h     |  1 +
 init/main.c                    |  1 +
 kernel/jump_label.c            | 49 ++++++++++++++++++++++++++++++++++
 4 files changed, 56 insertions(+)

Comments

kernel test robot Nov. 20, 2023, 9:38 p.m. UTC | #1 
Hi Valentin,

kernel test robot noticed the following build errors:

[auto build test ERROR on tip/x86/core]
[also build test ERROR on linus/master v6.7-rc2 next-20231120]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Valentin-Schneider/jump_label-module-Don-t-alloc-static_key_mod-for-__ro_after_init-keys/20231120-190044
base:   tip/x86/core
patch link:    https://lore.kernel.org/r/20231120105528.760306-2-vschneid%40redhat.com
patch subject: [PATCH 1/5] jump_label,module: Don't alloc static_key_mod for __ro_after_init keys
config: s390-allnoconfig (https://download.01.org/0day-ci/archive/20231121/202311210541.RAdnu4yL-lkp@intel.com/config)
compiler: s390-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231121/202311210541.RAdnu4yL-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202311210541.RAdnu4yL-lkp@intel.com/

All errors (new ones prefixed by >>):

   init/main.c: In function 'mark_readonly':
>> init/main.c:1406:17: error: implicit declaration of function 'jump_label_ro'; did you mean 'jump_label_lock'? [-Werror=implicit-function-declaration]
    1406 |                 jump_label_ro();
         |                 ^~~~~~~~~~~~~
         |                 jump_label_lock
   cc1: some warnings being treated as errors


vim +1406 init/main.c

  1394	
  1395	#ifdef CONFIG_STRICT_KERNEL_RWX
  1396	static void mark_readonly(void)
  1397	{
  1398		if (rodata_enabled) {
  1399			/*
  1400			 * load_module() results in W+X mappings, which are cleaned
  1401			 * up with call_rcu().  Let's make sure that queued work is
  1402			 * flushed so that we don't hit false positives looking for
  1403			 * insecure pages which are W+X.
  1404			 */
  1405			rcu_barrier();
> 1406			jump_label_ro();
  1407			mark_rodata_ro();
  1408			rodata_test();
  1409		} else
  1410			pr_info("Kernel memory protection disabled.\n");
  1411	}
  1412	#elif defined(CONFIG_ARCH_HAS_STRICT_KERNEL_RWX)
  1413	static inline void mark_readonly(void)
  1414	{
  1415		pr_warn("Kernel memory protection not selected by kernel config.\n");
  1416	}
  1417	#else
  1418	static inline void mark_readonly(void)
  1419	{
  1420		pr_warn("This architecture does not have kernel memory protection.\n");
  1421	}
  1422	#endif
  1423
kernel test robot Nov. 20, 2023, 10:47 p.m. UTC | #2 
Hi Valentin,

kernel test robot noticed the following build errors:

[auto build test ERROR on tip/x86/core]
[also build test ERROR on linus/master v6.7-rc2 next-20231120]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Valentin-Schneider/jump_label-module-Don-t-alloc-static_key_mod-for-__ro_after_init-keys/20231120-190044
base:   tip/x86/core
patch link:    https://lore.kernel.org/r/20231120105528.760306-2-vschneid%40redhat.com
patch subject: [PATCH 1/5] jump_label,module: Don't alloc static_key_mod for __ro_after_init keys
config: i386-allnoconfig (https://download.01.org/0day-ci/archive/20231121/202311210601.9dbatTYU-lkp@intel.com/config)
compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231121/202311210601.9dbatTYU-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202311210601.9dbatTYU-lkp@intel.com/

All errors (new ones prefixed by >>):

>> init/main.c:1406:3: error: call to undeclared function 'jump_label_ro'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
                   jump_label_ro();
                   ^
   init/main.c:1406:3: note: did you mean 'jump_label_lock'?
   include/linux/jump_label.h:315:20: note: 'jump_label_lock' declared here
   static inline void jump_label_lock(void) {}
                      ^
   1 error generated.


vim +/jump_label_ro +1406 init/main.c

  1394	
  1395	#ifdef CONFIG_STRICT_KERNEL_RWX
  1396	static void mark_readonly(void)
  1397	{
  1398		if (rodata_enabled) {
  1399			/*
  1400			 * load_module() results in W+X mappings, which are cleaned
  1401			 * up with call_rcu().  Let's make sure that queued work is
  1402			 * flushed so that we don't hit false positives looking for
  1403			 * insecure pages which are W+X.
  1404			 */
  1405			rcu_barrier();
> 1406			jump_label_ro();
  1407			mark_rodata_ro();
  1408			rodata_test();
  1409		} else
  1410			pr_info("Kernel memory protection disabled.\n");
  1411	}
  1412	#elif defined(CONFIG_ARCH_HAS_STRICT_KERNEL_RWX)
  1413	static inline void mark_readonly(void)
  1414	{
  1415		pr_warn("Kernel memory protection not selected by kernel config.\n");
  1416	}
  1417	#else
  1418	static inline void mark_readonly(void)
  1419	{
  1420		pr_warn("This architecture does not have kernel memory protection.\n");
  1421	}
  1422	#endif
  1423
diff mbox series

Patch

diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index db13bb620f527..c768de6f19a9a 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -180,6 +180,11 @@  static inline bool is_kernel_rodata(unsigned long addr)
 	       addr < (unsigned long)__end_rodata;
 }
 
+static inline bool is_kernel_ro_after_init(unsigned long addr)
+{
+	return addr >= (unsigned long)__start_ro_after_init &&
+	       addr < (unsigned long)__end_ro_after_init;
+}
 /**
  * is_kernel_inittext - checks if the pointer address is located in the
  *                      .init.text section
diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index f0a949b7c9733..88ef9e776af8d 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -216,6 +216,7 @@  extern struct jump_entry __start___jump_table[];
 extern struct jump_entry __stop___jump_table[];
 
 extern void jump_label_init(void);
+extern void jump_label_ro(void);
 extern void jump_label_lock(void);
 extern void jump_label_unlock(void);
 extern void arch_jump_label_transform(struct jump_entry *entry,
diff --git a/init/main.c b/init/main.c
index e24b0780fdff7..5f51d8b910dc1 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1407,6 +1407,7 @@  static void mark_readonly(void)
 		 * insecure pages which are W+X.
 		 */
 		rcu_barrier();
+		jump_label_ro();
 		mark_rodata_ro();
 		rodata_test();
 	} else
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index d9c822bbffb8d..661ef74dee9b7 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -530,6 +530,45 @@  void __init jump_label_init(void)
 	cpus_read_unlock();
 }
 
+static inline bool static_key_sealed(struct static_key *key)
+{
+	return (key->type & JUMP_TYPE_LINKED) && !(key->type & ~JUMP_TYPE_MASK);
+}
+
+static inline void static_key_seal(struct static_key *key)
+{
+	unsigned long type = key->type & JUMP_TYPE_TRUE;
+	key->type = JUMP_TYPE_LINKED | type;
+}
+
+void jump_label_ro(void)
+{
+	struct jump_entry *iter_start = __start___jump_table;
+	struct jump_entry *iter_stop = __stop___jump_table;
+	struct jump_entry *iter;
+
+	if (WARN_ON_ONCE(!static_key_initialized))
+		return;
+
+	cpus_read_lock();
+	jump_label_lock();
+
+	for (iter = iter_start; iter < iter_stop; iter++) {
+		struct static_key *iterk = jump_entry_key(iter);
+
+		if (!is_kernel_ro_after_init((unsigned long)iterk))
+			continue;
+
+		if (static_key_sealed(iterk))
+			continue;
+
+		static_key_seal(iterk);
+	}
+
+	jump_label_unlock();
+	cpus_read_unlock();
+}
+
 #ifdef CONFIG_MODULES
 
 enum jump_label_type jump_label_init_type(struct jump_entry *entry)
@@ -650,6 +689,15 @@  static int jump_label_add_module(struct module *mod)
 			static_key_set_entries(key, iter);
 			continue;
 		}
+
+		/*
+		 * If the key was sealed at init, then there's no need to keep a
+		 * a reference to its module entries - just patch them now and
+		 * be done with it.
+		 */
+		if (static_key_sealed(key))
+			goto do_poke;
+
 		jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
 		if (!jlm)
 			return -ENOMEM;
@@ -675,6 +723,7 @@  static int jump_label_add_module(struct module *mod)
 		static_key_set_linked(key);
 
 		/* Only update if we've changed from our initial state */
+do_poke:
 		if (jump_label_type(iter) != jump_label_init_type(iter))
 			__jump_label_update(key, iter, iter_stop, true);
 	}