6.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: Dan Williams <dan.j.williams@xxxxxxxxx>
[ Upstream commit 88d3917f82ed4215a2154432c26de1480a61b209 ]
Ira reports that removing cxl_mock_mem causes a crash with the following
trace:
BUG: kernel NULL pointer dereference, address: 0000000000000044
[..]
RIP: 0010:cxl_region_decode_reset+0x7f/0x180 [cxl_core]
[..]
Call Trace:
<TASK>
cxl_region_detach+0xe8/0x210 [cxl_core]
cxl_decoder_kill_region+0x27/0x40 [cxl_core]
cxld_unregister+0x29/0x40 [cxl_core]
devres_release_all+0xb8/0x110
device_unbind_cleanup+0xe/0x70
device_release_driver_internal+0x1d2/0x210
bus_remove_device+0xd7/0x150
device_del+0x155/0x3e0
device_unregister+0x13/0x60
devm_release_action+0x4d/0x90
? __pfx_unregister_port+0x10/0x10 [cxl_core]
delete_endpoint+0x121/0x130 [cxl_core]
devres_release_all+0xb8/0x110
device_unbind_cleanup+0xe/0x70
device_release_driver_internal+0x1d2/0x210
bus_remove_device+0xd7/0x150
device_del+0x155/0x3e0
? lock_release+0x142/0x290
cdev_device_del+0x15/0x50
cxl_memdev_unregister+0x54/0x70 [cxl_core]
This crash is due to the clearing out the cxl_memdev's driver context
(@cxlds) before the subsystem is done with it. This is ultimately due to
the region(s), that this memdev is a member, being torn down and expecting
to be able to de-reference @cxlds, like here:
static int cxl_region_decode_reset(struct cxl_region *cxlr, int count)
...
if (cxlds->rcd)
goto endpoint_reset;
...
Fix it by keeping the driver context valid until memdev-device
unregistration, and subsequently the entire stack of related
dependencies, unwinds.
Fixes: 9cc238c7a526 ("cxl/pci: Introduce cdevm_file_operations")
Reported-by: Ira Weiny <ira.weiny@xxxxxxxxx>
Reviewed-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>
Tested-by: Ira Weiny <ira.weiny@xxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/cxl/core/memdev.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
index a02061028b710..fed9573cf355e 100644
--- a/drivers/cxl/core/memdev.c
+++ b/drivers/cxl/core/memdev.c
@@ -559,8 +559,8 @@ static void cxl_memdev_unregister(void *_cxlmd)
struct cxl_memdev *cxlmd = _cxlmd;
struct device *dev = &cxlmd->dev;
- cxl_memdev_shutdown(dev);
cdev_device_del(&cxlmd->cdev, dev);
+ cxl_memdev_shutdown(dev);
put_device(dev);
}
--
2.42.0
