linux-kernel - [PATCH] iommufd: Do not allow _iommufd_object_alloc

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Message-ID: <20250710202354.1658511-1-nicolinc@nvidia.com>
Date: Thu, 10 Jul 2025 13:23:54 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: <jgg@...dia.com>, <kevin.tian@...el.com>
CC: <yilun.xu@...ux.intel.com>, <iommu@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH] iommufd: Do not allow _iommufd_object_alloc_ucmd if abort op is set

An abort op was introduced to allow its caller to invoke it within a lock
in the caller's function. On the other hand, _iommufd_object_alloc_ucmd()
would invoke the abort op in iommufd_object_abort_and_destroy() that must
be outside the caller's lock. So, these two cannot work together.

Add a validation in the _iommufd_object_alloc_ucmd(). Pick -EOPNOTSUPP to
reject the function call, indicating that the object allocator is buggy.

Suggested-by: Xu Yilun <yilun.xu@...ux.intel.com>
Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
---
 drivers/iommu/iommufd/main.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
index 0fb81a905cb1..69c2195e77ca 100644
--- a/drivers/iommu/iommufd/main.c
+++ b/drivers/iommu/iommufd/main.c
@@ -71,6 +71,15 @@ struct iommufd_object *_iommufd_object_alloc_ucmd(struct iommufd_ucmd *ucmd,
 	if (WARN_ON(ucmd->new_obj))
 		return ERR_PTR(-EBUSY);
 
+	/*
+	 * An abort op means that its caller needs to invoke it within a lock in
+	 * the caller. So it doesn't work with _iommufd_object_alloc_ucmd() that
+	 * will invoke the abort op in iommufd_object_abort_and_destroy(), which
+	 * must be outside the caller's lock.
+	 */
+	if (WARN_ON(iommufd_object_ops[type].abort))
+		return ERR_PTR(-EOPNOTSUPP);
+
 	new_obj = _iommufd_object_alloc(ucmd->ictx, size, type);
 	if (IS_ERR(new_obj))
 		return new_obj;
-- 
2.43.0