Re: [PATCH 1/2] cxl: fix possible null-ptr-deref in cxl_guest_init_afu|adapter()
From: Andrew Donnellan <hidden>
Date: 2022-11-21 05:20:14
On Fri, 2022-11-11 at 22:54 +0800, Yang Yingliang wrote:
If device_register() fails in cxl_register_afu|adapter(), the device is not added, device_unregister() can not be called in the error path, otherwise it will cause a null-ptr-deref because of removing not added device. As comment of device_register() says, it should use put_device() to give up the reference in the error path. So split device_unregister() into device_del() and put_device(), then goes to put dev when register fails.
The comment around device_add() is relevant too: Rule of thumb is: if device_add() succeeds, you should call device_del() when you want to get rid of it. If device_add() has *not* succeeded, use *only* put_device() to drop the reference count.
Fixes: 14baf4d9c739 ("cxl: Add guest-specific code")
Signed-off-by: Yang Yingliang <redacted>Thanks for the fix! Acked-by: Andrew Donnellan <redacted>
quoted hunk ↗ jump to hunk
--- drivers/misc/cxl/guest.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-)diff --git a/drivers/misc/cxl/guest.c b/drivers/misc/cxl/guest.c index 375f692ae9d6..fb95a2d5cef4 100644 --- a/drivers/misc/cxl/guest.c +++ b/drivers/misc/cxl/guest.c@@ -965,10 +965,10 @@ int cxl_guest_init_afu(struct cxl *adapter, intslice, struct device_node *afu_n * if it returns an error! */ if ((rc = cxl_register_afu(afu))) - goto err_put1; + goto err_put_dev; if ((rc = cxl_sysfs_afu_add(afu))) - goto err_put1; + goto err_del_dev; /* * pHyp doesn't expose the programming models supported by the@@ -984,7 +984,7 @@ int cxl_guest_init_afu(struct cxl *adapter, intslice, struct device_node *afu_n afu->modes_supported = CXL_MODE_DIRECTED; if ((rc = cxl_afu_select_best_mode(afu))) - goto err_put2; + goto err_remove_sysfs; adapter->afu[afu->slice] = afu;@@ -1004,10 +1004,12 @@ int cxl_guest_init_afu(struct cxl *adapter,int slice, struct device_node *afu_n return 0; -err_put2: +err_remove_sysfs: cxl_sysfs_afu_remove(afu); -err_put1: - device_unregister(&afu->dev); +err_del_dev: + device_del(&afu->dev); +err_put_dev: + put_device(&afu->dev); free = false; guest_release_serr_irq(afu); err2:@@ -1141,18 +1143,20 @@ struct cxl *cxl_guest_init_adapter(structdevice_node *np, struct platform_devic * even if it returns an error! */ if ((rc = cxl_register_adapter(adapter))) - goto err_put1; + goto err_put_dev; if ((rc = cxl_sysfs_adapter_add(adapter))) - goto err_put1; + goto err_del_dev; /* release the context lock as the adapter is configured */ cxl_adapter_context_unlock(adapter); return adapter; -err_put1: - device_unregister(&adapter->dev); +err_del_dev: + device_del(&adapter->dev); +err_put_dev: + put_device(&adapter->dev); free = false; cxl_guest_remove_chardev(adapter); err1:
-- Andrew Donnellan OzLabs, ADL Canberra ajd@linux.ibm.com IBM Australia Limited