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| author | Shivank Garg <shivankg@amd.com> | 2026-08-22 19:22:06 +0000 |
|---|---|---|
| committer | Vinod Koul <vkoul@kernel.org> | 2026-09-09 17:51:44 +0530 |
| commit | dc750422170a563c7a81f6e49d36bb02c62ae37f (patch) | |
| tree | ded5d46aeb2f27baee67de4313a59c7ed57ce054 /drivers | |
| parent | e873c74132f0c5f1452816cd9bb26208f0bba1e1 (diff) | |
| download | linux-stable-dc750422170a563c7a81f6e49d36bb02c62ae37f.tar.gz linux-stable-dc750422170a563c7a81f6e49d36bb02c62ae37f.zip | |
dmaengine: wait for RCU readers before releasing dma_device
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. This call will delay for a grace
period with dma_list_mutex held, which is safe and only teardown path is
delayed.
Fixes: 2ba05622b8b1 ("dmaengine: provide a common 'issue_pending_all' implementation")
Suggested-by: Sashiko <sashiko-bot@kernel.org>
Link: https://sashiko.dev/#/patchset/20260526-dmaengine-kref-fix-v2-0-3df60afac01d@amd.com
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Shivank Garg <shivankg@amd.com>
Link: https://patch.msgid.link/20260822-dmaengine-kref-fix-v5-4-d4a4ee47d927@amd.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/dma/dmaengine.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c index 872ae0d2e..c71763047 100644 --- a/drivers/dma/dmaengine.c +++ b/drivers/dma/dmaengine.c @@ -428,6 +428,7 @@ static void dma_device_release(struct kref *ref) list_del_rcu(&device->global_node); dma_channel_rebalance(); + synchronize_rcu(); if (device->device_release) device->device_release(device); |