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![Ollie Wild](/assets/img/avatar_default.png)
Remove the arg+env limit of MAX_ARG_PAGES by copying the strings directly from the old mm into the new mm. We create the new mm before the binfmt code runs, and place the new stack at the very top of the address space. Once the binfmt code runs and figures out where the stack should be, we move it downwards. It is a bit peculiar in that we have one task with two mm's, one of which is inactive. [a.p.zijlstra@chello.nl: limit stack size] Signed-off-by: Ollie Wild <aaw@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: <linux-arch@vger.kernel.org> Cc: Hugh Dickins <hugh@veritas.com> [bunk@stusta.de: unexport bprm_mm_init] Signed-off-by: Adrian Bunk <bunk@stusta.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
314 lines
7.5 KiB
C
314 lines
7.5 KiB
C
/*
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* mm/mprotect.c
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*
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* (C) Copyright 1994 Linus Torvalds
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* (C) Copyright 2002 Christoph Hellwig
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*
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* Address space accounting code <alan@redhat.com>
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* (C) Copyright 2002 Red Hat Inc, All Rights Reserved
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*/
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#include <linux/mm.h>
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#include <linux/hugetlb.h>
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#include <linux/slab.h>
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#include <linux/shm.h>
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#include <linux/mman.h>
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#include <linux/fs.h>
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#include <linux/highmem.h>
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#include <linux/security.h>
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#include <linux/mempolicy.h>
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#include <linux/personality.h>
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#include <linux/syscalls.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include <asm/uaccess.h>
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#include <asm/pgtable.h>
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#include <asm/cacheflush.h>
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#include <asm/tlbflush.h>
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static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
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unsigned long addr, unsigned long end, pgprot_t newprot,
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int dirty_accountable)
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{
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pte_t *pte, oldpte;
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spinlock_t *ptl;
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pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
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arch_enter_lazy_mmu_mode();
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do {
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oldpte = *pte;
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if (pte_present(oldpte)) {
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pte_t ptent;
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/* Avoid an SMP race with hardware updated dirty/clean
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* bits by wiping the pte and then setting the new pte
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* into place.
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*/
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ptent = ptep_get_and_clear(mm, addr, pte);
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ptent = pte_modify(ptent, newprot);
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/*
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* Avoid taking write faults for pages we know to be
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* dirty.
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*/
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if (dirty_accountable && pte_dirty(ptent))
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ptent = pte_mkwrite(ptent);
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set_pte_at(mm, addr, pte, ptent);
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lazy_mmu_prot_update(ptent);
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#ifdef CONFIG_MIGRATION
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} else if (!pte_file(oldpte)) {
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swp_entry_t entry = pte_to_swp_entry(oldpte);
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if (is_write_migration_entry(entry)) {
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/*
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* A protection check is difficult so
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* just be safe and disable write
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*/
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make_migration_entry_read(&entry);
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set_pte_at(mm, addr, pte,
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swp_entry_to_pte(entry));
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}
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#endif
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}
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} while (pte++, addr += PAGE_SIZE, addr != end);
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arch_leave_lazy_mmu_mode();
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pte_unmap_unlock(pte - 1, ptl);
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}
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static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud,
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unsigned long addr, unsigned long end, pgprot_t newprot,
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int dirty_accountable)
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{
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pmd_t *pmd;
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unsigned long next;
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pmd = pmd_offset(pud, addr);
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do {
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next = pmd_addr_end(addr, end);
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if (pmd_none_or_clear_bad(pmd))
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continue;
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change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable);
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} while (pmd++, addr = next, addr != end);
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}
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static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd,
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unsigned long addr, unsigned long end, pgprot_t newprot,
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int dirty_accountable)
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{
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pud_t *pud;
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unsigned long next;
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pud = pud_offset(pgd, addr);
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do {
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next = pud_addr_end(addr, end);
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if (pud_none_or_clear_bad(pud))
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continue;
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change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable);
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} while (pud++, addr = next, addr != end);
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}
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static void change_protection(struct vm_area_struct *vma,
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unsigned long addr, unsigned long end, pgprot_t newprot,
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int dirty_accountable)
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{
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struct mm_struct *mm = vma->vm_mm;
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pgd_t *pgd;
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unsigned long next;
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unsigned long start = addr;
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BUG_ON(addr >= end);
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pgd = pgd_offset(mm, addr);
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flush_cache_range(vma, addr, end);
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do {
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next = pgd_addr_end(addr, end);
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if (pgd_none_or_clear_bad(pgd))
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continue;
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change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable);
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} while (pgd++, addr = next, addr != end);
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flush_tlb_range(vma, start, end);
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}
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int
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mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
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unsigned long start, unsigned long end, unsigned long newflags)
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{
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struct mm_struct *mm = vma->vm_mm;
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unsigned long oldflags = vma->vm_flags;
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long nrpages = (end - start) >> PAGE_SHIFT;
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unsigned long charged = 0;
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pgoff_t pgoff;
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int error;
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int dirty_accountable = 0;
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if (newflags == oldflags) {
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*pprev = vma;
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return 0;
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}
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/*
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* If we make a private mapping writable we increase our commit;
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* but (without finer accounting) cannot reduce our commit if we
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* make it unwritable again.
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*
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* FIXME? We haven't defined a VM_NORESERVE flag, so mprotecting
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* a MAP_NORESERVE private mapping to writable will now reserve.
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*/
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if (newflags & VM_WRITE) {
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if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_SHARED))) {
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charged = nrpages;
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if (security_vm_enough_memory(charged))
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return -ENOMEM;
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newflags |= VM_ACCOUNT;
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}
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}
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/*
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* First try to merge with previous and/or next vma.
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*/
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pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
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*pprev = vma_merge(mm, *pprev, start, end, newflags,
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vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
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if (*pprev) {
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vma = *pprev;
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goto success;
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}
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*pprev = vma;
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if (start != vma->vm_start) {
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error = split_vma(mm, vma, start, 1);
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if (error)
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goto fail;
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}
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if (end != vma->vm_end) {
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error = split_vma(mm, vma, end, 0);
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if (error)
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goto fail;
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}
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success:
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/*
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* vm_flags and vm_page_prot are protected by the mmap_sem
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* held in write mode.
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*/
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vma->vm_flags = newflags;
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vma->vm_page_prot = protection_map[newflags &
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(VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)];
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if (vma_wants_writenotify(vma)) {
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vma->vm_page_prot = protection_map[newflags &
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(VM_READ|VM_WRITE|VM_EXEC)];
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dirty_accountable = 1;
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}
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if (is_vm_hugetlb_page(vma))
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hugetlb_change_protection(vma, start, end, vma->vm_page_prot);
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else
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change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable);
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vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
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vm_stat_account(mm, newflags, vma->vm_file, nrpages);
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return 0;
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fail:
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vm_unacct_memory(charged);
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return error;
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}
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asmlinkage long
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sys_mprotect(unsigned long start, size_t len, unsigned long prot)
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{
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unsigned long vm_flags, nstart, end, tmp, reqprot;
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struct vm_area_struct *vma, *prev;
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int error = -EINVAL;
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const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
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prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
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if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
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return -EINVAL;
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if (start & ~PAGE_MASK)
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return -EINVAL;
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if (!len)
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return 0;
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len = PAGE_ALIGN(len);
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end = start + len;
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if (end <= start)
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return -ENOMEM;
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if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM))
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return -EINVAL;
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reqprot = prot;
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/*
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* Does the application expect PROT_READ to imply PROT_EXEC:
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*/
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if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
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prot |= PROT_EXEC;
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vm_flags = calc_vm_prot_bits(prot);
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down_write(¤t->mm->mmap_sem);
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vma = find_vma_prev(current->mm, start, &prev);
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error = -ENOMEM;
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if (!vma)
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goto out;
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if (unlikely(grows & PROT_GROWSDOWN)) {
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if (vma->vm_start >= end)
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goto out;
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start = vma->vm_start;
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error = -EINVAL;
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if (!(vma->vm_flags & VM_GROWSDOWN))
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goto out;
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}
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else {
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if (vma->vm_start > start)
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goto out;
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if (unlikely(grows & PROT_GROWSUP)) {
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end = vma->vm_end;
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error = -EINVAL;
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if (!(vma->vm_flags & VM_GROWSUP))
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goto out;
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}
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}
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if (start > vma->vm_start)
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prev = vma;
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for (nstart = start ; ; ) {
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unsigned long newflags;
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/* Here we know that vma->vm_start <= nstart < vma->vm_end. */
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newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC));
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/* newflags >> 4 shift VM_MAY% in place of VM_% */
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if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {
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error = -EACCES;
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goto out;
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}
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error = security_file_mprotect(vma, reqprot, prot);
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if (error)
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goto out;
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tmp = vma->vm_end;
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if (tmp > end)
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tmp = end;
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error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
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if (error)
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goto out;
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nstart = tmp;
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if (nstart < prev->vm_end)
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nstart = prev->vm_end;
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if (nstart >= end)
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goto out;
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vma = prev->vm_next;
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if (!vma || vma->vm_start != nstart) {
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error = -ENOMEM;
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goto out;
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}
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}
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out:
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up_write(¤t->mm->mmap_sem);
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return error;
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}
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