mm: forbid splitting special mappings

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.

Link: https://lkml.kernel.org/r/20201013013416.390574-7-dima@arista.com
Signed-off-by: Dmitry Safonov <dima@arista.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Brian Geffon <bgeffon@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c
index fddd08a..3408269 100644 (file)
--- 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 debb899..cee5d04 100644 (file)
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -78,17 +78,9 @@ 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;
@@ -219,17 +211,6 @@ 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,
@@ -280,12 +261,6 @@ up_fail:
 /*
  * Create and map the vectors page for AArch32 tasks.
  */
-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);
-}
-
 enum aarch32_map {
        AA32_MAP_VECTORS, /* kuser helpers */
        AA32_MAP_SIGPAGE,
@@ -308,11 +283,10 @@ 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,
        },
 };
 
@@ -453,12 +427,6 @@ out:
 }
 #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,
@@ -468,7 +436,6 @@ 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 abb06ae..09e30eb 100644 (file)
--- 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 f9da5b1..6c9ec95 100644 (file)
--- a/arch/s390/kernel/vdso.c
+++ b/arch/s390/kernel/vdso.c
@@ -61,17 +61,8 @@ 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 9185cb1..0c942b3 100644 (file)
--- 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 886de79..10598e5 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3422,6 +3422,17 @@ 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,
@@ -3429,6 +3440,7 @@ 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 = {