From: Dmitry Safonov <dima@xxxxxxxxxx> Subject: 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@xxxxxxxxxx Signed-off-by: Dmitry Safonov <dima@xxxxxxxxxx> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Brian Geffon <bgeffon@xxxxxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: Dave Jiang <dave.jiang@xxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Jason Gunthorpe <jgg@xxxxxxxx> Cc: John Hubbard <jhubbard@xxxxxxxxxx> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: Ralph Campbell <rcampbell@xxxxxxxxxx> Cc: Russell King <linux@xxxxxxxxxxxxxxx> Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Will Deacon <will@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- 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, 17 insertions(+), 77 deletions(-) --- a/arch/arm64/kernel/vdso.c~mm-forbid-splitting-special-mappings +++ a/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) -{ - 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; - +static int vdso_mremap(const struct vm_special_mapping *sm, + struct vm_area_struct *new_vma) +{ current->mm->context.vdso = (void *)new_vma->vm_start; return 0; @@ -219,17 +211,6 @@ static vm_fault_t vvar_fault(const struc 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 [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 [AA64_MAP_VVAR] = { .name = "[vvar]", .fault = vvar_fault, - .mremap = vvar_mremap, }, [AA64_MAP_VDSO] = { .name = "[vdso]", --- a/arch/arm/kernel/vdso.c~mm-forbid-splitting-special-mappings +++ a/arch/arm/kernel/vdso.c @@ -50,15 +50,6 @@ static const struct vm_special_mapping v 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; --- a/arch/mips/vdso/genvdso.c~mm-forbid-splitting-special-mappings +++ a/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"); --- a/arch/s390/kernel/vdso.c~mm-forbid-splitting-special-mappings +++ a/arch/s390/kernel/vdso.c @@ -61,17 +61,8 @@ static vm_fault_t vdso_fault(const struc 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; } --- a/arch/x86/entry/vdso/vma.c~mm-forbid-splitting-special-mappings +++ a/arch/x86/entry/vdso/vma.c @@ -89,30 +89,14 @@ static void vdso_fix_landing(const struc 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 v static const struct vm_special_mapping vvar_mapping = { .name = "[vvar]", .fault = vvar_fault, - .mremap = vvar_mremap, }; /* --- a/mm/mmap.c~mm-forbid-splitting-special-mappings +++ a/mm/mmap.c @@ -3422,6 +3422,17 @@ static int special_mapping_mremap(struct 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 .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 = { _
