linux-kernel - [PATCH v4 1/4] module: Make module_enable_x() independent of CONFIG_ARCH_HAS_STRICT_MODULE

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Date:   Wed, 23 Feb 2022 10:00:58 +0100
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Luis Chamberlain <mcgrof@...nel.org>, linux-modules@...r.kernel.org
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v4 1/4] module: Make module_enable_x() independent of CONFIG_ARCH_HAS_STRICT_MODULE_RWX

module_enable_x() has nothing to do with CONFIG_ARCH_HAS_STRICT_MODULE_RWX
allthough by coincidence architectures who need module_enable_x() are
selection CONFIG_ARCH_HAS_STRICT_MODULE_RWX.

Enable module_enable_x() for everyone everytime. If an architecture
already has module text set executable, it's a no-op.

Don't check text_size alignment. When CONFIG_STRICT_MODULE_RWX is set
the verification is already done in frob_rodata(). When
CONFIG_STRICT_MODULE_RWX is not set it is not a big deal to have the
start of data as executable. Just make sure we entirely get the last
page when the boundary is not aligned.

And don't BUG on misaligned base as some architectures like nios2
use kmalloc() for allocating modules. So just bail out in that case.
If that's a problem, a page fault will occur later anyway.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 kernel/module/internal.h |  6 ++----
 kernel/module/main.c     | 12 +++++-------
 2 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/kernel/module/internal.h b/kernel/module/internal.h
index 3fc139d5074b..972bc811dcd2 100644
--- a/kernel/module/internal.h
+++ b/kernel/module/internal.h
@@ -23,9 +23,9 @@
 /*
  * Modules' sections will be aligned on page boundaries
  * to ensure complete separation of code and data, but
- * only when CONFIG_ARCH_HAS_STRICT_MODULE_RWX=y
+ * only when CONFIG_STRICT_MODULE_RWX=y
  */
-#ifdef CONFIG_ARCH_HAS_STRICT_MODULE_RWX
+#ifdef CONFIG_STRICT_MODULE_RWX
 # define debug_align(X) PAGE_ALIGN(X)
 #else
 # define debug_align(X) (X)
@@ -175,10 +175,8 @@ static inline struct module *mod_find(unsigned long addr)
 }
 #endif /* CONFIG_MODULES_TREE_LOOKUP */
 
-#ifdef CONFIG_ARCH_HAS_STRICT_MODULE_RWX
 void frob_text(const struct module_layout *layout, int (*set_memory)(unsigned long start,
 								     int num_pages));
-#endif /* CONFIG_ARCH_HAS_STRICT_MODULE_RWX */
 
 #ifdef CONFIG_STRICT_MODULE_RWX
 void module_enable_ro(const struct module *mod, bool after_init);
diff --git a/kernel/module/main.c b/kernel/module/main.c
index 0749afdc34b5..44e80b4e56db 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -1144,24 +1144,22 @@ resolve_symbol_wait(struct module *mod,
  * CONFIG_STRICT_MODULE_RWX block below because they are needed regardless of
  * whether we are strict.
  */
-#ifdef CONFIG_ARCH_HAS_STRICT_MODULE_RWX
 void frob_text(const struct module_layout *layout,
 	       int (*set_memory)(unsigned long start, int num_pages))
 {
-	BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
-	BUG_ON((unsigned long)layout->text_size & (PAGE_SIZE-1));
 	set_memory((unsigned long)layout->base,
-		   layout->text_size >> PAGE_SHIFT);
+		   PAGE_ALIGN(layout->text_size) >> PAGE_SHIFT);
 }
 
 static void module_enable_x(const struct module *mod)
 {
+	if (!PAGE_ALIGNED(mod->core_layout.base) ||
+	    !PAGE_ALIGNED(mod->init_layout.base))
+		return;
+
 	frob_text(&mod->core_layout, set_memory_x);
 	frob_text(&mod->init_layout, set_memory_x);
 }
-#else /* !CONFIG_ARCH_HAS_STRICT_MODULE_RWX */
-static void module_enable_x(const struct module *mod) { }
-#endif /* CONFIG_ARCH_HAS_STRICT_MODULE_RWX */
 
 void __weak module_memfree(void *module_region)
 {
-- 
2.34.1