From 20bd0198bebdd706bd4614b3933ef70d7c19618f Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Thu, 28 Sep 2023 18:02:07 -0700 Subject: [PATCH] cxl/mem: Fix shutdown order [ 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: 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 Reviewed-by: Davidlohr Bueso Reviewed-by: Dave Jiang Reviewed-by: Jonathan Cameron Reviewed-by: Ira Weiny Tested-by: Ira Weiny Signed-off-by: Dan Williams Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/cxl/core/memdev.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c index a9c317e32010..6673198870fe 100644 --- a/drivers/cxl/core/memdev.c +++ b/drivers/cxl/core/memdev.c @@ -139,10 +139,9 @@ static void cxl_memdev_unregister(void *_cxlmd) struct cdev *cdev = &cxlmd->cdev; const struct cdevm_file_operations *cdevm_fops; + cdev_device_del(&cxlmd->cdev, dev); cdevm_fops = container_of(cdev->ops, typeof(*cdevm_fops), fops); cdevm_fops->shutdown(dev); - - cdev_device_del(&cxlmd->cdev, dev); put_device(dev); }