Subject: [PATCH 10/13] modules, jitalloc: prepare to allocate executable memory as ROX

From: Mike Rapoport <[email-masked]>
Date: Thu, 1 Jun 2023 13:12:54 +0300

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

When executable memory will be allocated as ROX it won't be possible to
update it using memset() and memcpy().

Introduce jit_update_copy() and jit_update_set() APIs and use them in
modules loading code instead of memcpy() and memset().

Signed-off-by: Mike Rapoport (IBM) <[email-masked]>
---
 include/linux/jitalloc.h |  2 ++
 kernel/module/main.c     | 19 ++++++++++++++-----
 mm/jitalloc.c            | 20 ++++++++++++++++++++
 3 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/include/linux/jitalloc.h b/include/linux/jitalloc.h
index 7f8cafb3cfe9..0ba5ef785a85 100644
--- a/include/linux/jitalloc.h
+++ b/include/linux/jitalloc.h
@@ -55,6 +55,8 @@ struct jit_alloc_params *jit_alloc_arch_params(void);
 void jit_free(void *buf);
 void *jit_text_alloc(size_t len);
 void *jit_data_alloc(size_t len);
+void jit_update_copy(void *buf, void *new_buf, size_t len);
+void jit_update_set(void *buf, int c, size_t len);
 
 #ifdef CONFIG_JIT_ALLOC
 void jit_alloc_init(void);
diff --git a/kernel/module/main.c b/kernel/module/main.c
index 91477aa5f671..9f0711c42aa2 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -1197,9 +1197,19 @@ void __weak module_arch_freeing_init(struct module *mod)
 
 static void *module_memory_alloc(unsigned int size, enum mod_mem_type type)
 {
-	if (mod_mem_type_is_data(type))
-		return jit_data_alloc(size);
-	return jit_text_alloc(size);
+	void *p;
+
+	if (mod_mem_type_is_data(type)) {
+		p = jit_data_alloc(size);
+		if (p)
+			memset(p, 0, size);
+	} else {
+		p = jit_text_alloc(size);
+		if (p)
+			jit_update_set(p, 0, size);
+	}
+
+	return p;
 }
 
 static void module_memory_free(void *ptr, enum mod_mem_type type)
@@ -2223,7 +2233,6 @@ static int move_module(struct module *mod, struct load_info *info)
 			t = type;
 			goto out_enomem;
 		}
-		memset(ptr, 0, mod->mem[type].size);
 		mod->mem[type].base = ptr;
 	}
 
@@ -2251,7 +2260,7 @@ static int move_module(struct module *mod, struct load_info *info)
 				ret = -ENOEXEC;
 				goto out_enomem;
 			}
-			memcpy(dest, (void *)shdr->sh_addr, shdr->sh_size);
+			jit_update_copy(dest, (void *)shdr->sh_addr, shdr->sh_size);
 		}
 		/*
 		 * Update the userspace copy's ELF section address to point to
diff --git a/mm/jitalloc.c b/mm/jitalloc.c
index 16fd715d501a..a8ae64364d56 100644
--- a/mm/jitalloc.c
+++ b/mm/jitalloc.c
@@ -7,6 +7,16 @@
 
 static struct jit_alloc_params jit_alloc_params;
 
+static inline void jit_text_poke_copy(void *dst, const void *src, size_t len)
+{
+	memcpy(dst, src, len);
+}
+
+static inline void jit_text_poke_set(void *addr, int c, size_t len)
+{
+	memset(addr, c, len);
+}
+
 static void *jit_alloc(size_t len, unsigned int alignment, pgprot_t pgprot,
 		       unsigned long start, unsigned long end,
 		       unsigned long fallback_start, unsigned long fallback_end,
@@ -86,6 +96,16 @@ void *jit_data_alloc(size_t len)
 			 fallback_start, fallback_end, kasan);
 }
 
+void jit_update_copy(void *buf, void *new_buf, size_t len)
+{
+	jit_text_poke_copy(buf, new_buf, len);
+}
+
+void jit_update_set(void *addr, int c, size_t len)
+{
+	jit_text_poke_set(addr, c, len);
+}
+
 struct jit_alloc_params * __weak jit_alloc_arch_params(void)
 {
 	return NULL;
-- 
2.35.1