Commit c137381f authored by Suren Baghdasaryan's avatar Suren Baghdasaryan Committed by Linus Torvalds
Browse files

mm: lock a vma before stack expansion 



With recent changes necessitating mmap_lock to be held for write while
expanding a stack, per-VMA locks should follow the same rules and be
write-locked to prevent page faults into the VMA being expanded. Add
the necessary locking.

Cc: stable@vger.kernel.org
Signed-off-by: default avatarSuren Baghdasaryan <surenb@google.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7fcd473a

mm/mmap.c

+4 −0
Original line number Diff line number Diff line
@@ -1977,6 +1977,8 @@ static int expand_upwards(struct vm_area_struct *vma, unsigned long address) 
		return -ENOMEM;

	}



	/* Lock the VMA before expanding to prevent concurrent page faults */

	vma_start_write(vma);

	/*

	 * vma->vm_start/vm_end cannot change under us because the caller

	 * is required to hold the mmap_lock in read mode.  We need the
@@ -2064,6 +2066,8 @@ int expand_downwards(struct vm_area_struct *vma, unsigned long address) 
		return -ENOMEM;

	}



	/* Lock the VMA before expanding to prevent concurrent page faults */

	vma_start_write(vma);

	/*

	 * vma->vm_start/vm_end cannot change under us because the caller

	 * is required to hold the mmap_lock in read mode.  We need the