linux-kernel - [PATCH] PCI: endpoint: Fix use after free in pci_epf_remove

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Date:   Mon, 21 Jun 2021 16:00:58 +0900
From:   Shunsuke Mie <mie@...l.co.jp>
To:     kishon@...com
Cc:     lorenzo.pieralisi@....com, bhelgaas@...gle.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, mie@...l.co.jp
Subject: [PATCH] PCI: endpoint: Fix use after free in pci_epf_remove_cfs()

All of entries are freed in a loop, however, the freed entry is accessed
by list_del() after the loop.

When epf driver that includes pci-epf-test unload, the pci_epf_remove_cfs()
is called, and occurred the use after free. Therefore, kernel panics
randomly after or while the module unloading.

I tested this patch with r8a77951-Salvator-xs boards.

Fixes: ef1433f ("PCI: endpoint: Create configfs entry for each pci_epf_device_id table entry")
Signed-off-by: Shunsuke Mie <mie@...l.co.jp>
---
 drivers/pci/endpoint/pci-epf-core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/endpoint/pci-epf-core.c b/drivers/pci/endpoint/pci-epf-core.c
index e9289d10f822..538e902b0ba6 100644
--- a/drivers/pci/endpoint/pci-epf-core.c
+++ b/drivers/pci/endpoint/pci-epf-core.c
@@ -202,8 +202,10 @@ static void pci_epf_remove_cfs(struct pci_epf_driver *driver)
 		return;
 
 	mutex_lock(&pci_epf_mutex);
-	list_for_each_entry_safe(group, tmp, &driver->epf_group, group_entry)
+	list_for_each_entry_safe(group, tmp, &driver->epf_group, group_entry) {
+		list_del(&group->group_entry);
 		pci_ep_cfs_remove_epf_group(group);
+	}
 	list_del(&driver->epf_group);
 	mutex_unlock(&pci_epf_mutex);
 }
-- 
2.17.1