This is a note to let you know that I've just added the patch titled
dmaengine: idxd: Let probe fail when workqueue cannot be enabled
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
dmaengine-idxd-let-probe-fail-when-workqueue-cannot-be-enabled.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b51b75f0604f17c0f6f3b6f68f1a521a5cc6b04f Mon Sep 17 00:00:00 2001
From: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Date: Wed, 7 Dec 2022 14:52:20 -0800
Subject: dmaengine: idxd: Let probe fail when workqueue cannot be enabled
From: Reinette Chatre <reinette.chatre@xxxxxxxxx>
commit b51b75f0604f17c0f6f3b6f68f1a521a5cc6b04f upstream.
The workqueue is enabled when the appropriate driver is loaded and
disabled when the driver is removed. When the driver is removed it
assumes that the workqueue was enabled successfully and proceeds to
free allocations made during workqueue enabling.
Failure during workqueue enabling does not prevent the driver from
being loaded. This is because the error path within drv_enable_wq()
returns success unless a second failure is encountered
during the error path. By returning success it is possible to load
the driver even if the workqueue cannot be enabled and
allocations that do not exist are attempted to be freed during
driver remove.
Some examples of problematic flows:
(a)
idxd_dmaengine_drv_probe() -> drv_enable_wq() -> idxd_wq_request_irq():
In above flow, if idxd_wq_request_irq() fails then
idxd_wq_unmap_portal() is called on error exit path, but
drv_enable_wq() returns 0 because idxd_wq_disable() succeeds. The
driver is thus loaded successfully.
idxd_dmaengine_drv_remove()->drv_disable_wq()->idxd_wq_unmap_portal()
Above flow on driver unload triggers the WARN in devm_iounmap() because
the device resource has already been removed during error path of
drv_enable_wq().
(b)
idxd_dmaengine_drv_probe() -> drv_enable_wq() -> idxd_wq_request_irq():
In above flow, if idxd_wq_request_irq() fails then
idxd_wq_init_percpu_ref() is never called to initialize the percpu
counter, yet the driver loads successfully because drv_enable_wq()
returns 0.
idxd_dmaengine_drv_remove()->__idxd_wq_quiesce()->percpu_ref_kill():
Above flow on driver unload triggers a BUG when attempting to drop the
initial ref of the uninitialized percpu ref:
BUG: kernel NULL pointer dereference, address: 0000000000000010
Fix the drv_enable_wq() error path by returning the original error that
indicates failure of workqueue enabling. This ensures that the probe
fails when an error is encountered and the driver remove paths are only
attempted when the workqueue was enabled successfully.
Fixes: 1f2bb40337f0 ("dmaengine: idxd: move wq_enable() to device.c")
Signed-off-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
Reviewed-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/e8d8116e5efa0fd14fadc5adae6ffd319f0e5ff1.1670452419.git.reinette.chatre@xxxxxxxxx
Signed-off-by: Vinod Koul <vkoul@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/dma/idxd/device.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- a/drivers/dma/idxd/device.c
+++ b/drivers/dma/idxd/device.c
@@ -1391,8 +1391,7 @@ err_res_alloc:
err_irq:
idxd_wq_unmap_portal(wq);
err_map_portal:
- rc = idxd_wq_disable(wq, false);
- if (rc < 0)
+ if (idxd_wq_disable(wq, false))
dev_dbg(dev, "wq %s disable failed\n", dev_name(wq_confdev(wq)));
err:
return rc;
Patches currently in stable-queue which might be from reinette.chatre@xxxxxxxxx are
queue-6.1/dmaengine-idxd-do-not-call-dmx-tx-callbacks-during-workqueue-disable.patch
queue-6.1/dmaengine-idxd-let-probe-fail-when-workqueue-cannot-be-enabled.patch
queue-6.1/dmaengine-idxd-prevent-use-after-free-on-completion-memory.patch
