From: Dmitry Safonov <dima@xxxxxxxxxx> Subject: mm/mremap: for MREMAP_DONTUNMAP check security_vm_enough_memory_mm() Currently memory is accounted post-mremap() with MREMAP_DONTUNMAP, which may break overcommit policy. So, check if there's enough memory before doing actual VMA copy. Don't unset VM_ACCOUNT on MREMAP_DONTUNMAP. By semantics, such mremap() is actually a memory allocation. That also simplifies the error-path a little. Also, as it's memory allocation on success don't reset hiwater_vm value. Link: https://lkml.kernel.org/r/20201013013416.390574-3-dima@xxxxxxxxxx Fixes: commit e346b3813067 ("mm/mremap: add MREMAP_DONTUNMAP to mremap()") 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> --- mm/mremap.c | 36 +++++++++++++----------------------- 1 file changed, 13 insertions(+), 23 deletions(-) --- a/mm/mremap.c~mm-mremap-for-mremap_dontunmap-check-security_vm_enough_memory_mm +++ a/mm/mremap.c @@ -515,11 +515,19 @@ static unsigned long move_vma(struct vm_ if (err) return err; + if (unlikely(flags & MREMAP_DONTUNMAP && vm_flags & VM_ACCOUNT)) { + if (security_vm_enough_memory_mm(mm, new_len >> PAGE_SHIFT)) + return -ENOMEM; + } + new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT); new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff, &need_rmap_locks); - if (!new_vma) + if (!new_vma) { + if (unlikely(flags & MREMAP_DONTUNMAP && vm_flags & VM_ACCOUNT)) + vm_unacct_memory(new_len >> PAGE_SHIFT); return -ENOMEM; + } moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len, need_rmap_locks); @@ -548,7 +556,7 @@ static unsigned long move_vma(struct vm_ } /* Conceal VM_ACCOUNT so old reservation is not undone */ - if (vm_flags & VM_ACCOUNT) { + if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) { vma->vm_flags &= ~VM_ACCOUNT; excess = vma->vm_end - vma->vm_start - old_len; if (old_addr > vma->vm_start && @@ -573,34 +581,16 @@ static unsigned long move_vma(struct vm_ untrack_pfn_moved(vma); if (unlikely(!err && (flags & MREMAP_DONTUNMAP))) { - if (vm_flags & VM_ACCOUNT) { - /* Always put back VM_ACCOUNT since we won't unmap */ - vma->vm_flags |= VM_ACCOUNT; - - vm_acct_memory(new_len >> PAGE_SHIFT); - } - - /* - * VMAs can actually be merged back together in copy_vma - * calling merge_vma. This can happen with anonymous vmas - * which have not yet been faulted, so if we were to consider - * this VMA split we'll end up adding VM_ACCOUNT on the - * next VMA, which is completely unrelated if this VMA - * was re-merged. - */ - if (split && new_vma == vma) - split = 0; - /* We always clear VM_LOCKED[ONFAULT] on the old vma */ vma->vm_flags &= VM_LOCKED_CLEAR_MASK; /* Because we won't unmap we don't need to touch locked_vm */ - goto out; + return new_addr; } if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) { /* OOM: unable to split vma, just get accounts right */ - if (vm_flags & VM_ACCOUNT) + if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) vm_acct_memory(new_len >> PAGE_SHIFT); excess = 0; } @@ -609,7 +599,7 @@ static unsigned long move_vma(struct vm_ mm->locked_vm += new_len >> PAGE_SHIFT; *locked = true; } -out: + mm->hiwater_vm = hiwater_vm; /* Restore VM_ACCOUNT if one or two pieces of vma left */ _
