[PATCH] iommu/iova: Add NULL check in iova_magazine_free()

[Lynn Liu <liulynn@google.com>]

From: lynn <liulynn@google.com>

When iova_domain_init_rcaches() fails to allocate an iova_magazine
during the initialization of per-cpu rcaches, it jumps to out_err and
calls free_iova_rcaches() for cleanup.

In free_iova_rcaches(), the code iterates through all possible CPUs to
free both cpu_rcache->loaded and cpu_rcache->prev. However, if the
original allocation failed mid-way through the CPU loop, the pointers
for the remaining CPUs remain NULL.

Since kmem_cache_free() does not explicitly handle NULL pointers like
kfree() does, passing these NULL pointers leads to a kernel paging
request fault.

Add a NULL check in iova_magazine_free() to safely handle partially
initialized rcaches in error paths.

Signed-off-by: lynn <liulynn@google.com>
---
 drivers/iommu/iova.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index 18f839721813..e026be5e068b 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -611,7 +611,8 @@ static struct iova_magazine *iova_magazine_alloc(gfp_t flags)
 
 static void iova_magazine_free(struct iova_magazine *mag)
 {
-	kmem_cache_free(iova_magazine_cache, mag);
+	if (mag)
+		kmem_cache_free(iova_magazine_cache, mag);
 }
 
 static void
-- 
2.53.0.273.g2a3d683680-goog