Prevent a possible endless loop with DMAPOOL_DEBUG enabled if a buggy
driver corrupts DMA pool memory.
Signed-off-by: Tony Battersby <to...@cybernetics.com>
---
--- linux/mm/dmapool.c.orig 2018-08-02 10:14:25.000000000 -0400
+++ linux/mm/dmapool.c 2018-08-02 10:16:17.000000000 -0400
@@ -449,16 +449,35 @@ void dma_pool_free(struct dma_pool *pool
{
void *page_vaddr = vaddr - offset;
unsigned int chain = page->dma_free_o;
+ size_t total_free = 0;
+
while (chain < pool->allocation) {
- if (chain != offset) {
- chain = *(int *)(page_vaddr + chain);
- continue;
+ if (unlikely(chain == offset)) {
+ spin_unlock_irqrestore(&pool->lock, flags);
+ dev_err(pool->dev,
+ "dma_pool_free %s, dma %pad already
free\n",
+ pool->name, &dma);
+ return;
+ }
+
+ /*
+ * The calculation of the number of blocks per
+ * allocation is actually more complicated than this
+ * because of the boundary value. But this comparison
+ * does not need to be exact; it just needs to prevent
+ * an endless loop in case a buggy driver causes a
+ * circular loop in the freelist.
+ */
+ total_free += pool->size;
+ if (unlikely(total_free >= pool->allocation)) {
+ spin_unlock_irqrestore(&pool->lock, flags);
+ dev_err(pool->dev,
+ "dma_pool_free %s, freelist
corrupted\n",
+ pool->name);
+ return;
}
- spin_unlock_irqrestore(&pool->lock, flags);
- dev_err(pool->dev,
- "dma_pool_free %s, dma %pad already free\n",
- pool->name, &dma);
- return;
+
+ chain = *(int *)(page_vaddr + chain);
}
}
memset(vaddr, POOL_POISON_FREED, pool->size);
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