[PATCH] mm: fix incorrect vbq reference in purge_fragmented_block

[zhaoyang.huang]

From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>

Broken vbq->free reported on a v6.6 based system which is caused
by invalid vbq->lock protect over vbq->free in purge_fragmented_block.
This should be introduced by the Fixes below which ignored vbq->lock
matter.

Fixes: fc1e0d980037 ("mm/vmalloc: prevent stale TLBs in fully utilized blocks")

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
---
 mm/vmalloc.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 22aa63f4ef63..112b50431725 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2614,9 +2614,10 @@ static void free_vmap_block(struct vmap_block *vb)
 }
 
 static bool purge_fragmented_block(struct vmap_block *vb,
-		struct vmap_block_queue *vbq, struct list_head *purge_list,
-		bool force_purge)
+		struct list_head *purge_list, bool force_purge)
 {
+	struct vmap_block_queue *vbq;
+
 	if (vb->free + vb->dirty != VMAP_BBMAP_BITS ||
 	    vb->dirty == VMAP_BBMAP_BITS)
 		return false;
@@ -2625,6 +2626,8 @@ static bool purge_fragmented_block(struct vmap_block *vb,
 	if (!(force_purge || vb->free < VMAP_PURGE_THRESHOLD))
 		return false;
 
+	vbq = container_of(addr_to_vb_xa(vb->va->va_start),
+		struct vmap_block_queue, vmap_blocks);
 	/* prevent further allocs after releasing lock */
 	WRITE_ONCE(vb->free, 0);
 	/* prevent purging it again */
@@ -2664,7 +2667,7 @@ static void purge_fragmented_blocks(int cpu)
 			continue;
 
 		spin_lock(&vb->lock);
-		purge_fragmented_block(vb, vbq, &purge, true);
+		purge_fragmented_block(vb, &purge, true);
 		spin_unlock(&vb->lock);
 	}
 	rcu_read_unlock();
@@ -2801,7 +2804,7 @@ static void _vm_unmap_aliases(unsigned long start, unsigned long end, int flush)
 			 * not purgeable, check whether there is dirty
 			 * space to be flushed.
 			 */
-			if (!purge_fragmented_block(vb, vbq, &purge_list, false) &&
+			if (!purge_fragmented_block(vb, &purge_list, false) &&
 			    vb->dirty_max && vb->dirty != VMAP_BBMAP_BITS) {
 				unsigned long va_start = vb->va->va_start;
 				unsigned long s, e;
-- 
2.25.1