Subject: [PATCH 13/13] x86/jitalloc: make memory allocated for code ROX

From: Mike Rapoport <[email-masked]>
Date: Thu, 1 Jun 2023 13:12:57 +0300

From: "Mike Rapoport (IBM)" <[email-masked]>

When STRICT_KERNEL_RWX or STRICT_MODULE_RWX is enabled, force text
allocations to use KERNEL_PAGE_ROX.

Signed-off-by: Mike Rapoport (IBM) <[email-masked]>
---
 arch/Kconfig             |  3 +++
 arch/x86/Kconfig         |  1 +
 arch/x86/kernel/ftrace.c |  3 ---
 arch/x86/mm/init.c       |  6 ++++++
 include/linux/jitalloc.h |  2 ++
 mm/jitalloc.c            | 21 +++++++++++++++++++++
 6 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 479a7b8be191..e7c4b01307d7 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1307,6 +1307,9 @@ config STRICT_MODULE_RWX
 	  and non-text memory will be made non-executable. This provides
 	  protection against certain security exploits (e.g. writing to text)
 
+config ARCH_HAS_TEXT_POKE
+	def_bool n
+
 # select if the architecture provides an asm/dma-direct.h header
 config ARCH_HAS_PHYS_TO_DMA
 	bool
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index fac4add6ce16..e1a512f557de 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -96,6 +96,7 @@ config X86
 	select ARCH_HAS_SET_DIRECT_MAP
 	select ARCH_HAS_STRICT_KERNEL_RWX
 	select ARCH_HAS_STRICT_MODULE_RWX
+	select ARCH_HAS_TEXT_POKE
 	select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
 	select ARCH_HAS_SYSCALL_WRAPPER
 	select ARCH_HAS_UBSAN_SANITIZE_ALL
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index d50595f2c1a6..bd4dd8974ee6 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -313,7 +313,6 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
 	unsigned long call_offset;
 	unsigned long jmp_offset;
 	unsigned long offset;
-	unsigned long npages;
 	unsigned long size;
 	unsigned long *ptr;
 	void *trampoline;
@@ -350,7 +349,6 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
 		return 0;
 
 	*tramp_size = size + RET_SIZE + sizeof(void *);
-	npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE);
 
 	/* Copy ftrace_caller onto the trampoline memory */
 	ret = text_poke_copy(trampoline, (void *)start_offset, size);
@@ -416,7 +414,6 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
 	/* ALLOC_TRAMP flags lets us know we created it */
 	ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;
 
-	set_memory_rox((unsigned long)trampoline, npages);
 	return (unsigned long)trampoline;
 fail:
 	tramp_free(trampoline);
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index ffaf9a3840ce..c314738991fa 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -1127,6 +1127,12 @@ struct jit_alloc_params *jit_alloc_arch_params(void)
 	jit_alloc_params.text.start = MODULES_VADDR + get_jit_load_offset();
 	jit_alloc_params.text.end = MODULES_END;
 
+	if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX) ||
+	    IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) {
+		jit_alloc_params.text.pgprot = PAGE_KERNEL_ROX;
+		jit_alloc_params.flags |= JIT_ALLOC_USE_TEXT_POKE;
+	}
+
 	return &jit_alloc_params;
 }
 #endif /* CONFIG_JIT_ALLOC */
diff --git a/include/linux/jitalloc.h b/include/linux/jitalloc.h
index 0ba5ef785a85..0e29e87acefe 100644
--- a/include/linux/jitalloc.h
+++ b/include/linux/jitalloc.h
@@ -15,9 +15,11 @@
 /**
  * enum jit_alloc_flags - options for executable memory allocations
  * @JIT_ALLOC_KASAN_SHADOW:	allocate kasan shadow
+ * @JIT_ALLOC_USE_TEXT_POKE:	use text poking APIs to update memory
  */
 enum jit_alloc_flags {
 	JIT_ALLOC_KASAN_SHADOW	= (1 << 0),
+	JIT_ALLOC_USE_TEXT_POKE	= (1 << 1),
 };
 
 /**
diff --git a/mm/jitalloc.c b/mm/jitalloc.c
index a8ae64364d56..15d1067faf3f 100644
--- a/mm/jitalloc.c
+++ b/mm/jitalloc.c
@@ -7,6 +7,26 @@
 
 static struct jit_alloc_params jit_alloc_params;
 
+#ifdef CONFIG_ARCH_HAS_TEXT_POKE
+#include <asm/text-patching.h>
+
+static inline void jit_text_poke_copy(void *dst, const void *src, size_t len)
+{
+	if (jit_alloc_params.flags & JIT_ALLOC_USE_TEXT_POKE)
+		text_poke_copy(dst, src, len);
+	else
+		memcpy(dst, src, len);
+}
+
+static inline void jit_text_poke_set(void *addr, int c, size_t len)
+{
+	if (jit_alloc_params.flags & JIT_ALLOC_USE_TEXT_POKE)
+		text_poke_set(addr, c, len);
+	else
+		memset(addr, c, len);
+}
+
+#else
 static inline void jit_text_poke_copy(void *dst, const void *src, size_t len)
 {
 	memcpy(dst, src, len);
@@ -16,6 +36,7 @@ static inline void jit_text_poke_set(void *addr, int c, size_t len)
 {
 	memset(addr, c, len);
 }
+#endif
 
 static void *jit_alloc(size_t len, unsigned int alignment, pgprot_t pgprot,
 		       unsigned long start, unsigned long end,
-- 
2.35.1