@@ -317,6 +317,12 @@ extern unsigned int kobjsize(const void *objp);
#define VM_HIGH_ARCH_4 BIT(VM_HIGH_ARCH_BIT_4)
#endif /* CONFIG_ARCH_USES_HIGH_VMA_FLAGS */
+#ifdef CONFIG_ARCH_ENABLE_DENY_WRITE_EXEC
+#define VM_WAS_WRITE BIT(37) /* only with ARCH_USES_HIGH_VMA_FLAGS */
+#else
+#define VM_WAS_WRITE VM_NONE
+#endif
+
#ifdef CONFIG_ARCH_HAS_PKEYS
# define VM_PKEY_SHIFT VM_HIGH_ARCH_BIT_0
# define VM_PKEY_BIT0 VM_HIGH_ARCH_0 /* A protection key is a 4-bit value */
@@ -141,10 +141,16 @@ static inline bool arch_validate_flags(unsigned long flags)
static inline unsigned long
calc_vm_prot_bits(unsigned long prot, unsigned long pkey)
{
- return _calc_vm_trans(prot, PROT_READ, VM_READ ) |
+ unsigned long vm_flags =
+ _calc_vm_trans(prot, PROT_READ, VM_READ ) |
_calc_vm_trans(prot, PROT_WRITE, VM_WRITE) |
_calc_vm_trans(prot, PROT_EXEC, VM_EXEC) |
arch_calc_vm_prot_bits(prot, pkey);
+
+ if (vm_flags & VM_WRITE)
+ vm_flags |= VM_WAS_WRITE;
+
+ return vm_flags;
}
/*
@@ -822,6 +822,10 @@ config ARCH_USES_HIGH_VMA_FLAGS
config ARCH_HAS_PKEYS
bool
+config ARCH_ENABLE_DENY_WRITE_EXEC
+ bool
+ depends on ARCH_USES_HIGH_VMA_FLAGS
+
config PERCPU_STATS
bool "Collect percpu memory statistics"
help
In order to support a memory-deny-write-execute policy for mprotect() and prevent a previously writeable mapping from being made executable, track the past VM_WRITE permission via a new VM_WAS_WRITE flag that is not cleared on permission change. VM_WAS_WRITE is a high VMA flag and since not all architectures may want this feature, only define it if CONFIG_ARCH_ENABLE_DENY_WRITE_EXEC is selected, otherwise it is VM_NONE (zero). Note that the new VM_WAS_WRITE flag would prevent merging of an always read-only vma with a previously writeable vma that was made read-only. I don't consider this a common case and even if we somehow allow such merging, it would be confusing for the user if a read-only vma inherits a VM_WAS_WRITE flag or the VM_WAS_WRITE flag is dropped. Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Andrew Morton <akpm@linux-foundation.org> --- include/linux/mm.h | 6 ++++++ include/linux/mman.h | 8 +++++++- mm/Kconfig | 4 ++++ 3 files changed, 17 insertions(+), 1 deletion(-)