Commit ad8ee77e authored by Dmitry Safonov's avatar Dmitry Safonov Committed by Linus Torvalds
Browse files

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@arista.com


Fixes: commit e346b381 ("mm/mremap: add MREMAP_DONTUNMAP to mremap()")
Signed-off-by: default avatarDmitry 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 51df7bcb

mm/mremap.c

+13 −23
Original line number Diff line number Diff line
@@ -515,11 +515,19 @@ static unsigned long move_vma(struct vm_area_struct *vma, 
	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_area_struct *vma, 
	}



	/* 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_area_struct *vma, 
		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_area_struct *vma, 
		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 */