[PATCH v2 6/6] dma-debug: Ensure mappings are created and released with matching attributes

Leon Romanovsky
2026-05-01T06:35:53Z

The DMA API expects that callers use the same attributes when mapping
and unmapping. Add tracking to verify this and catch mismatches.

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
kernel/dma/debug.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)

diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index 3dfed51c3d9aa..c38efc1ac8d6c 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -1074,6 +1074,29 @@ static void check_unmap(struct dma_debug_entry *ref)
type2name[entry->type]);
}

+ /*
+ * This may be no bug in reality - but DMA API still expects
+ * that entry is unmapped with same attributes as it was mapped.
+ *
+ * DMA_ATTR_UNMAP_VALID lists the attributes that must be identical
+ * between map and unmap. Any attribute outside this set (e.g.
+ * DMA_ATTR_NO_WARN, DMA_ATTR_SKIP_CPU_SYNC) is allowed to differ.
+ */
+#define DMA_ATTR_UNMAP_VALID \
+ (DMA_ATTR_NO_KERNEL_MAPPING | DMA_ATTR_FORCE_CONTIGUOUS | \
+ DMA_ATTR_MMIO | DMA_ATTR_REQUIRE_COHERENT | DMA_ATTR_PRIVILEGED | \
+ DMA_ATTR_CC_SHARED)
+ if ((ref->attrs & DMA_ATTR_UNMAP_VALID) !=
+ (entry->attrs & DMA_ATTR_UNMAP_VALID)) {
+ err_printk(ref->dev, entry,
+ "device driver frees "
+ "DMA memory with different attributes "
+ "[device address=0x%016llx] [size=%llu bytes] "
+ "[mapped with 0x%lx] [unmapped with 0x%lx]\n",
+ ref->dev_addr, ref->size, entry->attrs, ref->attrs);
+ }
+#undef DMA_ATTR_UNMAP_VALID
+
hash_bucket_del(entry);
put_hash_bucket(bucket, flags);

--
2.53.0