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List: linux-aio
Subject: [PATCH 6/6] mm: Forbid splitting special mappings
From: Dmitry Safonov <dima () arista ! com>
Date: 2020-10-13 1:34:16
Message-ID: 20201013013416.390574-7-dima () arista ! com
[Download RAW message or body]
Don't allow splitting of vm_special_mapping's.
It affects vdso/vvar areas. Uprobes have only one page in xol_area so
they aren't affected.
Those restrictions were enforced by checks in .mremap() callbacks.
Restrict resizing with generic .split() callback.
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
arch/arm/kernel/vdso.c | 9 ---------
arch/arm64/kernel/vdso.c | 41 +++------------------------------------
arch/mips/vdso/genvdso.c | 4 ----
arch/s390/kernel/vdso.c | 11 +----------
arch/x86/entry/vdso/vma.c | 17 ----------------
mm/mmap.c | 12 ++++++++++++
6 files changed, 16 insertions(+), 78 deletions(-)
diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c
index fddd08a6e063..3408269d19c7 100644
--- a/arch/arm/kernel/vdso.c
+++ b/arch/arm/kernel/vdso.c
@@ -50,15 +50,6 @@ static const struct vm_special_mapping vdso_data_mapping = {
static int vdso_mremap(const struct vm_special_mapping *sm,
struct vm_area_struct *new_vma)
{
- unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
- unsigned long vdso_size;
-
- /* without VVAR page */
- vdso_size = (vdso_total_pages - 1) << PAGE_SHIFT;
-
- if (vdso_size != new_size)
- return -EINVAL;
-
current->mm->context.vdso = new_vma->vm_start;
return 0;
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index d4202a32abc9..a1a4220a405b 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -82,17 +82,9 @@ static union {
} vdso_data_store __page_aligned_data;
struct vdso_data *vdso_data = vdso_data_store.data;
-static int __vdso_remap(enum vdso_abi abi,
- const struct vm_special_mapping *sm,
- struct vm_area_struct *new_vma)
+static int vdso_mremap(const struct vm_special_mapping *sm,
+ struct vm_area_struct *new_vma)
{
- unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
- unsigned long vdso_size = vdso_info[abi].vdso_code_end -
- vdso_info[abi].vdso_code_start;
-
- if (vdso_size != new_size)
- return -EINVAL;
-
current->mm->context.vdso = (void *)new_vma->vm_start;
return 0;
@@ -223,17 +215,6 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
return vmf_insert_pfn(vma, vmf->address, pfn);
}
-static int vvar_mremap(const struct vm_special_mapping *sm,
- struct vm_area_struct *new_vma)
-{
- unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
-
- if (new_size != VVAR_NR_PAGES * PAGE_SIZE)
- return -EINVAL;
-
- return 0;
-}
-
static int __setup_additional_pages(enum vdso_abi abi,
struct mm_struct *mm,
struct linux_binprm *bprm,
@@ -284,14 +265,6 @@ static int __setup_additional_pages(enum vdso_abi abi,
/*
* Create and map the vectors page for AArch32 tasks.
*/
-#ifdef CONFIG_COMPAT_VDSO
-static int aarch32_vdso_mremap(const struct vm_special_mapping *sm,
- struct vm_area_struct *new_vma)
-{
- return __vdso_remap(VDSO_ABI_AA32, sm, new_vma);
-}
-#endif /* CONFIG_COMPAT_VDSO */
-
enum aarch32_map {
AA32_MAP_VECTORS, /* kuser helpers */
#ifdef CONFIG_COMPAT_VDSO
@@ -313,11 +286,10 @@ static struct vm_special_mapping aarch32_vdso_maps[] = {
[AA32_MAP_VVAR] = {
.name = "[vvar]",
.fault = vvar_fault,
- .mremap = vvar_mremap,
},
[AA32_MAP_VDSO] = {
.name = "[vdso]",
- .mremap = aarch32_vdso_mremap,
+ .mremap = vdso_mremap,
},
#endif /* CONFIG_COMPAT_VDSO */
[AA32_MAP_SIGPAGE] = {
@@ -465,12 +437,6 @@ int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
}
#endif /* CONFIG_COMPAT */
-static int vdso_mremap(const struct vm_special_mapping *sm,
- struct vm_area_struct *new_vma)
-{
- return __vdso_remap(VDSO_ABI_AA64, sm, new_vma);
-}
-
enum aarch64_map {
AA64_MAP_VVAR,
AA64_MAP_VDSO,
@@ -480,7 +446,6 @@ static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
[AA64_MAP_VVAR] = {
.name = "[vvar]",
.fault = vvar_fault,
- .mremap = vvar_mremap,
},
[AA64_MAP_VDSO] = {
.name = "[vdso]",
diff --git a/arch/mips/vdso/genvdso.c b/arch/mips/vdso/genvdso.c
index abb06ae04b40..09e30eb4be86 100644
--- a/arch/mips/vdso/genvdso.c
+++ b/arch/mips/vdso/genvdso.c
@@ -263,10 +263,6 @@ int main(int argc, char **argv)
fprintf(out_file, " const struct vm_special_mapping *sm,\n");
fprintf(out_file, " struct vm_area_struct *new_vma)\n");
fprintf(out_file, "{\n");
- fprintf(out_file, " unsigned long new_size =\n");
- fprintf(out_file, " new_vma->vm_end - new_vma->vm_start;\n");
- fprintf(out_file, " if (vdso_image.size != new_size)\n");
- fprintf(out_file, " return -EINVAL;\n");
fprintf(out_file, " current->mm->context.vdso =\n");
fprintf(out_file, " (void *)(new_vma->vm_start);\n");
fprintf(out_file, " return 0;\n");
diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c
index c4baefaa6e34..291ead792d64 100644
--- a/arch/s390/kernel/vdso.c
+++ b/arch/s390/kernel/vdso.c
@@ -59,17 +59,8 @@ static vm_fault_t vdso_fault(const struct vm_special_mapping *sm,
static int vdso_mremap(const struct vm_special_mapping *sm,
struct vm_area_struct *vma)
{
- unsigned long vdso_pages;
-
- vdso_pages = vdso64_pages;
-
- if ((vdso_pages << PAGE_SHIFT) != vma->vm_end - vma->vm_start)
- return -EINVAL;
-
- if (WARN_ON_ONCE(current->mm != vma->vm_mm))
- return -EFAULT;
-
current->mm->context.vdso_base = vma->vm_start;
+
return 0;
}
diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 9185cb1d13b9..0c942b31825d 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -89,30 +89,14 @@ static void vdso_fix_landing(const struct vdso_image *image,
static int vdso_mremap(const struct vm_special_mapping *sm,
struct vm_area_struct *new_vma)
{
- unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
const struct vdso_image *image = current->mm->context.vdso_image;
- if (image->size != new_size)
- return -EINVAL;
-
vdso_fix_landing(image, new_vma);
current->mm->context.vdso = (void __user *)new_vma->vm_start;
return 0;
}
-static int vvar_mremap(const struct vm_special_mapping *sm,
- struct vm_area_struct *new_vma)
-{
- const struct vdso_image *image = new_vma->vm_mm->context.vdso_image;
- unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
-
- if (new_size != -image->sym_vvar_start)
- return -EINVAL;
-
- return 0;
-}
-
#ifdef CONFIG_TIME_NS
static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
{
@@ -252,7 +236,6 @@ static const struct vm_special_mapping vdso_mapping = {
static const struct vm_special_mapping vvar_mapping = {
.name = "[vvar]",
.fault = vvar_fault,
- .mremap = vvar_mremap,
};
/*
diff --git a/mm/mmap.c b/mm/mmap.c
index a62cb3ccafce..41100f6505ff 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3389,6 +3389,17 @@ static int special_mapping_mremap(struct vm_area_struct *new_vma,
return 0;
}
+static int special_mapping_split(struct vm_area_struct *vma, unsigned long addr)
+{
+ /*
+ * Forbid splitting special mappings - kernel has expectations over
+ * the number of pages in mapping. Together with VM_DONTEXPAND
+ * the size of vma should stay the same over the special mapping's
+ * lifetime.
+ */
+ return -EINVAL;
+}
+
static const struct vm_operations_struct special_mapping_vmops = {
.close = special_mapping_close,
.fault = special_mapping_fault,
@@ -3396,6 +3407,7 @@ static const struct vm_operations_struct special_mapping_vmops = {
.name = special_mapping_name,
/* vDSO code relies that VVAR can't be accessed remotely */
.access = NULL,
+ .may_split = special_mapping_split,
};
static const struct vm_operations_struct legacy_special_mapping_vmops = {
--
2.28.0
--
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