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: [email protected] Signed-off-by: Suren Baghdasaryan <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
wafgo · Jul 8, 2023 · c137381 · c137381
1 parent 7fcd473
commit c137381
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/mm/mmap.c b/mm/mmap.c
@@ -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