From: Jeff Xu <[email protected]> munmap(2) unmap VMAs in the given address range. Sealing will prevent unintended munmap(2) call.
What this patch does: When a munmap(2) is invoked, if one of its VMAs has MM_SEAL_MUNMAP set from previous mseal(2) call, this munmap(2) will fail, without any VMA modified. This patch is based on following: 1. At syscall entry point: SYSCALL_DEFINE2(munmap, ...) Pass checkSeals = MM_SEAL_MUNMAP into __vm_munmap(), in turn, to do_vmi_munmap(). Of all the call paths that call into do_vmi_munmap(), this is the only place where checkSeals = MM_SEAL_MUNMAP. The rest has checkSeals = 0. 2. In do_vmi_munmap(), calls can_modify_mm() before any update is made to VMAs. Signed-off-by: Jeff Xu <[email protected]> --- include/linux/mm.h | 2 +- mm/mmap.c | 21 +++++++++++++-------- mm/mremap.c | 5 +++-- 3 files changed, 17 insertions(+), 11 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index b09df8501987..f2f316522f2a 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3279,7 +3279,7 @@ extern unsigned long do_mmap(struct file *file, unsigned long addr, unsigned long pgoff, unsigned long *populate, struct list_head *uf); extern int do_vmi_munmap(struct vma_iterator *vmi, struct mm_struct *mm, unsigned long start, size_t len, struct list_head *uf, - bool unlock); + bool unlock, unsigned long checkSeals); extern int do_munmap(struct mm_struct *, unsigned long, size_t, struct list_head *uf); extern int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int behavior); diff --git a/mm/mmap.c b/mm/mmap.c index 414ac31aa9fa..62d592f16f45 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2601,6 +2601,7 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma, * @len: The length of the range to munmap * @uf: The userfaultfd list_head * @unlock: set to true if the user wants to drop the mmap_lock on success + * @checkSeals: seal type to check. * * 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 @@ -2611,7 +2612,7 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma, */ int do_vmi_munmap(struct vma_iterator *vmi, struct mm_struct *mm, unsigned long start, size_t len, struct list_head *uf, - bool unlock) + bool unlock, unsigned long checkSeals) { unsigned long end; struct vm_area_struct *vma; @@ -2623,6 +2624,9 @@ int do_vmi_munmap(struct vma_iterator *vmi, struct mm_struct *mm, if (end == start) return -EINVAL; + if (!can_modify_mm(mm, start, end, checkSeals)) + return -EACCES; + /* arch_unmap() might do unmaps itself. */ arch_unmap(mm, start, end); @@ -2650,7 +2654,7 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, { VMA_ITERATOR(vmi, mm, start); - return do_vmi_munmap(&vmi, mm, start, len, uf, false); + return do_vmi_munmap(&vmi, mm, start, len, uf, false, 0); } unsigned long mmap_region(struct file *file, unsigned long addr, @@ -2684,7 +2688,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, } /* Unmap any existing mapping in the area */ - if (do_vmi_munmap(&vmi, mm, addr, len, uf, false)) + if (do_vmi_munmap(&vmi, mm, addr, len, uf, false, 0)) return -ENOMEM; /* @@ -2909,7 +2913,8 @@ unsigned long mmap_region(struct file *file, unsigned long addr, return error; } -static int __vm_munmap(unsigned long start, size_t len, bool unlock) +static int __vm_munmap(unsigned long start, size_t len, bool unlock, + unsigned long checkSeals) { int ret; struct mm_struct *mm = current->mm; @@ -2919,7 +2924,7 @@ static int __vm_munmap(unsigned long start, size_t len, bool unlock) if (mmap_write_lock_killable(mm)) return -EINTR; - ret = do_vmi_munmap(&vmi, mm, start, len, &uf, unlock); + ret = do_vmi_munmap(&vmi, mm, start, len, &uf, unlock, checkSeals); if (ret || !unlock) mmap_write_unlock(mm); @@ -2929,14 +2934,14 @@ static int __vm_munmap(unsigned long start, size_t len, bool unlock) int vm_munmap(unsigned long start, size_t len) { - return __vm_munmap(start, len, false); + return __vm_munmap(start, len, false, 0); } EXPORT_SYMBOL(vm_munmap); SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len) { addr = untagged_addr(addr); - return __vm_munmap(addr, len, true); + return __vm_munmap(addr, len, true, MM_SEAL_MUNMAP); } @@ -3168,7 +3173,7 @@ int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags) if (ret) goto limits_failed; - ret = do_vmi_munmap(&vmi, mm, addr, len, &uf, 0); + ret = do_vmi_munmap(&vmi, mm, addr, len, &uf, 0, 0); if (ret) goto munmap_failed; diff --git a/mm/mremap.c b/mm/mremap.c index 056478c106ee..ac363937f8c4 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -715,7 +715,8 @@ static unsigned long move_vma(struct vm_area_struct *vma, } vma_iter_init(&vmi, mm, old_addr); - if (!do_vmi_munmap(&vmi, mm, old_addr, old_len, uf_unmap, false)) { + if (!do_vmi_munmap(&vmi, mm, old_addr, old_len, uf_unmap, false, + 0)) { /* OOM: unable to split vma, just get accounts right */ if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) vm_acct_memory(old_len >> PAGE_SHIFT); @@ -1009,7 +1010,7 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, } ret = do_vmi_munmap(&vmi, mm, addr + new_len, old_len - new_len, - &uf_unmap, true); + &uf_unmap, true, 0); if (ret) goto out; -- 2.42.0.655.g421f12c284-goog
