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From:   Ira Weiny <ira.weiny@intel.com>
Date:   Thu, 16 Nov 2023 16:03:29 -0800
Subject: [PATCH] cxl/cdat: Free correct buffer on checksum error
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Message-Id: <20231116-fix-cdat-devm-free-v1-1-b148b40707d7@intel.com>
To:     Davidlohr Bueso <dave@stgolabs.net>,
        Jonathan Cameron <jonathan.cameron@huawei.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Alison Schofield <alison.schofield@intel.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Dan Williams <dan.j.williams@intel.com>
Cc:     linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org,
        Fan Ni <nifan.cxl@gmail.com>, Ira Weiny <ira.weiny@intel.com>
Precedence: bulk

The new 6.7-rc1 kernel now checks the checksum on CDAT data.  While
using a branch of Fan's DCD qemu work (and specifying DCD devices), the
following splat was observed.

	WARNING: CPU: 1 PID: 1384 at drivers/base/devres.c:1064 devm_kfree+0x4f/0x60
	...
	RIP: 0010:devm_kfree+0x4f/0x60
	...
 	? devm_kfree+0x4f/0x60
 	read_cdat_data+0x1a0/0x2a0 [cxl_core]
 	cxl_port_probe+0xdf/0x200 [cxl_port]
	...

The issue in qemu is still unknown but the spat is a straight forward
bug in the CDAT checksum processing code.  Use a CDAT buffer variable to
ensure the devm_free() works correctly on error.

Cc: jonathan.cameron@huawei.com
Cc: Fan Ni <nifan.cxl@gmail.com>
Fixes: 670e4e88f3b1 ("cxl: Add checksum verification to CDAT from CXL")
Cc: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
---
 drivers/cxl/core/pci.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
index eff20e83d0a6..5aaa0b36c42a 100644
--- a/drivers/cxl/core/pci.c
+++ b/drivers/cxl/core/pci.c
@@ -620,7 +620,7 @@ void read_cdat_data(struct cxl_port *port)
 	struct pci_dev *pdev = NULL;
 	struct cxl_memdev *cxlmd;
 	size_t cdat_length;
-	void *cdat_table;
+	void *cdat_table, *cdat_buf;
 	int rc;
 
 	if (is_cxl_memdev(uport)) {
@@ -651,16 +651,16 @@ void read_cdat_data(struct cxl_port *port)
 		return;
 	}
 
-	cdat_table = devm_kzalloc(dev, cdat_length + sizeof(__le32),
+	cdat_buf = devm_kzalloc(dev, cdat_length + sizeof(__le32),
 				  GFP_KERNEL);
-	if (!cdat_table)
+	if (!cdat_buf)
 		return;
 
-	rc = cxl_cdat_read_table(dev, cdat_doe, cdat_table, &cdat_length);
+	rc = cxl_cdat_read_table(dev, cdat_doe, cdat_buf, &cdat_length);
 	if (rc)
 		goto err;
 
-	cdat_table = cdat_table + sizeof(__le32);
+	cdat_table = cdat_buf + sizeof(__le32);
 	if (cdat_checksum(cdat_table, cdat_length))
 		goto err;
 
@@ -670,7 +670,7 @@ void read_cdat_data(struct cxl_port *port)
 
 err:
 	/* Don't leave table data allocated on error */
-	devm_kfree(dev, cdat_table);
+	devm_kfree(dev, cdat_buf);
 	dev_err(dev, "Failed to read/validate CDAT.\n");
 }
 EXPORT_SYMBOL_NS_GPL(read_cdat_data, CXL);

---
base-commit: 7475e51b87969e01a6812eac713a1c8310372e8a
change-id: 20231116-fix-cdat-devm-free-b47d32b4b833

Best regards,
-- 
Ira Weiny <ira.weiny@intel.com>