linux-kernel - [PATCH net] pds_core: remove write-after-free of client

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Message-ID: <20250425203857.71547-1-shannon.nelson@amd.com>
Date: Fri, 25 Apr 2025 13:38:57 -0700
From: Shannon Nelson <shannon.nelson@....com>
To: <andrew+netdev@...n.ch>, <brett.creeley@....com>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>
CC: Shannon Nelson <shannon.nelson@....com>
Subject: [PATCH net] pds_core: remove write-after-free of client_id

A use-after-free error popped up in stress testing:

[Mon Apr 21 21:21:33 2025] BUG: KFENCE: use-after-free write in pdsc_auxbus_dev_del+0xef/0x160 [pds_core]
[Mon Apr 21 21:21:33 2025] Use-after-free write at 0x000000007013ecd1 (in kfence-#47):
[Mon Apr 21 21:21:33 2025]  pdsc_auxbus_dev_del+0xef/0x160 [pds_core]
[Mon Apr 21 21:21:33 2025]  pdsc_remove+0xc0/0x1b0 [pds_core]
[Mon Apr 21 21:21:33 2025]  pci_device_remove+0x24/0x70
[Mon Apr 21 21:21:33 2025]  device_release_driver_internal+0x11f/0x180
[Mon Apr 21 21:21:33 2025]  driver_detach+0x45/0x80
[Mon Apr 21 21:21:33 2025]  bus_remove_driver+0x83/0xe0
[Mon Apr 21 21:21:33 2025]  pci_unregister_driver+0x1a/0x80

The actual device uninit usually happens on a separate thread
scheduled after this code runs, but there is no guarantee of order
of thread execution, so this could be a problem.  There's no
actual need to clear the client_id at this point, so simply
remove the offending code.

Fixes: 10659034c622 ("pds_core: add the aux client API")
Signed-off-by: Shannon Nelson <shannon.nelson@....com>
---
 drivers/net/ethernet/amd/pds_core/auxbus.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/net/ethernet/amd/pds_core/auxbus.c b/drivers/net/ethernet/amd/pds_core/auxbus.c
index c9aac27883a3..92f359f2b449 100644
--- a/drivers/net/ethernet/amd/pds_core/auxbus.c
+++ b/drivers/net/ethernet/amd/pds_core/auxbus.c
@@ -186,7 +186,6 @@ void pdsc_auxbus_dev_del(struct pdsc *cf, struct pdsc *pf,
 	pds_client_unregister(pf, padev->client_id);
 	auxiliary_device_delete(&padev->aux_dev);
 	auxiliary_device_uninit(&padev->aux_dev);
-	padev->client_id = 0;
 	*pd_ptr = NULL;
 
 	mutex_unlock(&pf->config_lock);
-- 
2.17.1