From patchwork series 418974

https://patchwork.ozlabs.org//project/linuxppc-dev/list/?series=418974

Author: Fox Snowpatch

arch/powerpc/include/asm/mmu_context.h

@@ -260,15 +260,6 @@ static inline void enter_lazy_tlb(struct mm_struct *mm,
 
 extern void arch_exit_mmap(struct mm_struct *mm);
 
-static inline void arch_unmap(struct mm_struct *mm,
-			      unsigned long start, unsigned long end)
-{
-	unsigned long vdso_base = (unsigned long)mm->context.vdso;
-
-	if (start <= vdso_base && vdso_base < end)
-		mm->context.vdso = NULL;
-}
-
 #ifdef CONFIG_PPC_MEM_KEYS
 bool arch_vma_access_permitted(struct vm_area_struct *vma, bool write,
 			       bool execute, bool foreign);

arch/powerpc/kernel/vdso.c

@@ -81,6 +81,21 @@ static int vdso64_mremap(const struct vm_special_mapping *sm, struct vm_area_str
 	return vdso_mremap(sm, new_vma, &vdso64_end - &vdso64_start);
 }
 
+static void vdso_close(const struct vm_special_mapping *sm, struct vm_area_struct *vma)
+{
+	struct mm_struct *mm = vma->vm_mm;
+
+	/*
+	 * close() is called for munmap() but also for mremap(). In the mremap()
+	 * case the vdso pointer has already been updated by the mremap() hook
+	 * above, so it must not be set to NULL here.
+	 */
+	if (vma->vm_start != (unsigned long)mm->context.vdso)
+		return;
+
+	mm->context.vdso = NULL;
+}
+
 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 			     struct vm_area_struct *vma, struct vm_fault *vmf);
 
@@ -92,11 +107,13 @@ static struct vm_special_mapping vvar_spec __ro_after_init = {
 static struct vm_special_mapping vdso32_spec __ro_after_init = {
 	.name = "[vdso]",
 	.mremap = vdso32_mremap,
+	.close = vdso_close,
 };
 
 static struct vm_special_mapping vdso64_spec __ro_after_init = {
 	.name = "[vdso]",
 	.mremap = vdso64_mremap,
+	.close = vdso_close,
 };
 
 #ifdef CONFIG_TIME_NS
@@ -197,13 +214,6 @@ static int __arch_setup_additional_pages(struct linux_binprm *bprm, int uses_int
 	/* Add required alignment. */
 	vdso_base = ALIGN(vdso_base, VDSO_ALIGNMENT);
 
-	/*
-	 * Put vDSO base into mm struct. We need to do this before calling
-	 * install_special_mapping or the perf counter mmap tracking code
-	 * will fail to recognise it as a vDSO.
-	 */
-	mm->context.vdso = (void __user *)vdso_base + vvar_size;
-
 	vma = _install_special_mapping(mm, vdso_base, vvar_size,
 				       VM_READ | VM_MAYREAD | VM_IO |
 				       VM_DONTDUMP | VM_PFNMAP, &vvar_spec);
@@ -223,10 +233,15 @@ static int __arch_setup_additional_pages(struct linux_binprm *bprm, int uses_int
 	vma = _install_special_mapping(mm, vdso_base + vvar_size, vdso_size,
 				       VM_READ | VM_EXEC | VM_MAYREAD |
 				       VM_MAYWRITE | VM_MAYEXEC, vdso_spec);
-	if (IS_ERR(vma))
+	if (IS_ERR(vma)) {
 		do_munmap(mm, vdso_base, vvar_size, NULL);
+		return PTR_ERR(vma);
+	}
+
+	// Now that the mappings are in place, set the mm VDSO pointer
+	mm->context.vdso = (void __user *)vdso_base + vvar_size;
 
-	return PTR_ERR_OR_ZERO(vma);
+	return 0;
 }
 
 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
@@ -240,8 +255,6 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 		return -EINTR;
 
 	rc = __arch_setup_additional_pages(bprm, uses_interp);
-	if (rc)
-		mm->context.vdso = NULL;
 
 	mmap_write_unlock(mm);
 	return rc;

arch/x86/include/asm/mmu_context.h

@@ -232,11 +232,6 @@ static inline bool is_64bit_mm(struct mm_struct *mm)
 }
 #endif
 
-static inline void arch_unmap(struct mm_struct *mm, unsigned long start,
-			      unsigned long end)
-{
-}
-
 /*
  * We only want to enforce protection keys on the current process
  * because we effectively have no access to PKRU for other

include/asm-generic/mm_hooks.h

@@ -1,8 +1,8 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 /*
- * Define generic no-op hooks for arch_dup_mmap, arch_exit_mmap
- * and arch_unmap to be included in asm-FOO/mmu_context.h for any
- * arch FOO which doesn't need to hook these.
+ * Define generic no-op hooks for arch_dup_mmap and arch_exit_mmap
+ * to be included in asm-FOO/mmu_context.h for any arch FOO which
+ * doesn't need to hook these.
  */
 #ifndef _ASM_GENERIC_MM_HOOKS_H
 #define _ASM_GENERIC_MM_HOOKS_H
@@ -17,11 +17,6 @@ static inline void arch_exit_mmap(struct mm_struct *mm)
 {
 }
 
-static inline void arch_unmap(struct mm_struct *mm,
-			unsigned long start, unsigned long end)
-{
-}
-
 static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,
 		bool write, bool execute, bool foreign)
 {

include/linux/mm_types.h

@@ -1313,6 +1313,9 @@ struct vm_special_mapping {
 
 	int (*mremap)(const struct vm_special_mapping *sm,
 		     struct vm_area_struct *new_vma);
+
+	void (*close)(const struct vm_special_mapping *sm,
+		      struct vm_area_struct *vma);
 };
 
 enum tlb_flush_reason {

mm/mmap.c

@@ -2789,7 +2789,7 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
  *
  * This function takes a @mas that is either pointing to the previous VMA or set
  * to MA_START and sets it up to remove the mapping(s).  The @len will be
- * aligned and any arch_unmap work will be preformed.
+ * aligned.
  *
  * Return: 0 on success and drops the lock if so directed, error and leaves the
  * lock held otherwise.
@@ -2809,16 +2809,12 @@ int do_vmi_munmap(struct vma_iterator *vmi, struct mm_struct *mm,
 		return -EINVAL;
 
 	/*
-	 * Check if memory is sealed before arch_unmap.
-	 * Prevent unmapping a sealed VMA.
+	 * Check if memory is sealed, prevent unmapping a sealed VMA.
 	 * can_modify_mm assumes we have acquired the lock on MM.
 	 */
 	if (unlikely(!can_modify_mm(mm, start, end)))
 		return -EPERM;
 
-	 /* arch_unmap() might do unmaps itself.  */
-	arch_unmap(mm, start, end);
-
 	/* Find the first overlapping VMA */
 	vma = vma_find(vmi, end);
 	if (!vma) {
@@ -3232,14 +3228,12 @@ int do_vma_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	struct mm_struct *mm = vma->vm_mm;
 
 	/*
-	 * Check if memory is sealed before arch_unmap.
-	 * Prevent unmapping a sealed VMA.
+	 * Check if memory is sealed, prevent unmapping a sealed VMA.
 	 * can_modify_mm assumes we have acquired the lock on MM.
 	 */
 	if (unlikely(!can_modify_mm(mm, start, end)))
 		return -EPERM;
 
-	arch_unmap(mm, start, end);
 	return do_vmi_align_munmap(vmi, vma, mm, start, end, uf, unlock);
 }
 
@@ -3620,10 +3614,16 @@ void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
 static vm_fault_t special_mapping_fault(struct vm_fault *vmf);
 
 /*
+ * Close hook, called for unmap() and on the old vma for mremap().
+ *
  * Having a close hook prevents vma merging regardless of flags.
  */
 static void special_mapping_close(struct vm_area_struct *vma)
 {
+	const struct vm_special_mapping *sm = vma->vm_private_data;
+
+	if (sm->close)
+		sm->close(sm, vma);
 }
 
 static const char *special_mapping_name(struct vm_area_struct *vma)