Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

50358c25 · Linus Torvalds <[email protected]> · 2025-05-09 11:30:26 -07:00

Pull arm64 fix from Catalin Marinas:
 "Move the arm64_use_ng_mappings variable from the .bss to the .data
  section as it is accessed very early during boot with the MMU off and
  before the .bss has been initialised.

  This could lead to incorrect idmap page table"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: cpufeature: Move arm64_use_ng_mappings to the .data section to prevent wrong idmap generation

Commit: 50358c251eae19a2b2fc54b6944e362ef2fefff0
Parents: 3013c33d · 363cd2b8

Merge commit. Changes below are compared with the first parent: 3013c33d.

Changes

1 files changed · +8 −1

File	Status	Add	Del	Content
arch/arm64/kernel/cpufeature.c	modified	+8	−1	View file

arch/arm64/kernel/cpufeature.c

View file

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 9c4d6d5..4c46d80 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -114,7 +114,14 @@ static struct arm64_cpu_capabilities const __ro_after_init *cpucap_ptrs[ARM64_NC
 
 DECLARE_BITMAP(boot_cpucaps, ARM64_NCAPS);
 
-bool arm64_use_ng_mappings = false;
+/*
+ * arm64_use_ng_mappings must be placed in the .data section, otherwise it
+ * ends up in the .bss section where it is initialized in early_map_kernel()
+ * after the MMU (with the idmap) was enabled. create_init_idmap() - which
+ * runs before early_map_kernel() and reads the variable via PTE_MAYBE_NG -
+ * may end up generating an incorrect idmap page table attributes.
+ */
+bool arm64_use_ng_mappings __read_mostly = false;
 EXPORT_SYMBOL(arm64_use_ng_mappings);
 
 DEFINE_PER_CPU_READ_MOSTLY(const char *, this_cpu_vector) = vectors;