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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 7sHZt1VHiPqXaZon9jt/800L20+HQmOZdWnU3n0vh80S/+8yDtGmyWLd1a+aQ2OuCimRyurejlzEqg7PbCxYv/n22vwD9j4NrqcDkOjmJrnpqJN6apwJma3C4L+JZu2nMCHiDwMSxdmsjVTNHFtnnHk9QYEimy6pU6WfSjRI39d5H6U4h9igwZJQyObHNmh5y/FoL/i+eQQ5LQpbmtfqVrF3uKtPvosuawjpMu3nBGj7m0oCM/mgp/XaXws3u40tQfHFVpHjlPRDPysSQlbmPZJdSBNBqotrh5JjIwdTilsHJZaUYbZogIVMFfY8nOV5ihto+xiZBvOuo9kjtTdQi12Sg43pe87mJKf7i2qXckueUwycbdWgnlYQuwPeIlIXFTP4E4G/PQOYpnNrk8RiVWIqGc0ukdOILLV0olGA/DZ1g1YbuWBEr9a/quyxIxxG X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Aug 2026 15:49:44.8568 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 9289b9d5-3c41-4284-b15d-08defbadfe64 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CH1PEPF0000AD78.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR12MB5662 dma_issue_pending_all() walks the dma_device_list with list_for_each_entry_rcu() under rcu_read_lock(). dma_device_release() unlinks the device with list_del_rcu() and then calls device->device_release() (which in many drivers, such as plx_dma.c, directly calls kfree()). Because there is no grace period between unlinking the device and freeing it, concurrent RCU readers in dma_issue_pending_all() can access the device after it has been freed. The lockless walk originally relied on clients holding a dmaengine reference to pin the provider module, and therefore the device, for as long as they might traverse the list. Commit 8ad342a86359 ("dmaengine: Add reference counting to dma_device struct") decoupled the dma_device lifetime from the module reference, so the device can now be released while a reader is still walking the list. Add synchronize_rcu() before the device is freed, so RCU readers are guaranteed to have finished. Keep it unconditional: providers that do not implement device_release() free the device themselves once dma_async_device_unregister() returns, so they need the same grace period. Fixes: 2ba05622b8b1 ("dmaengine: provide a common 'issue_pending_all' implementation") Suggested-by: Sashiko Link: https://sashiko.dev/#/patchset/20260526-dmaengine-kref-fix-v2-0-3df60afac01d@amd.com Signed-off-by: Shivank Garg --- drivers/dma/dmaengine.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c index bf491eb10596..29b128aa0bea 100644 --- a/drivers/dma/dmaengine.c +++ b/drivers/dma/dmaengine.c @@ -429,6 +429,12 @@ static void dma_device_release(struct kref *ref) list_del_rcu(&device->global_node); dma_channel_rebalance(); + /* + * Wait for RCU readers (e.g. dma_issue_pending_all()) that may still + * be traversing dma_device_list before the device is freed. + */ + synchronize_rcu(); + if (device->device_release) device->device_release(device); } -- 2.43.0