Re: [PATCH] misc: ocxl: fix possible double free in ocxl_file_register_afu
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2022-04-20 22:54:10
Also in:
lkml
Hangyu Hua [off-list ref] writes:
info_release() will be called in device_unregister() when info->dev's reference count is 0. So there is no need to call ocxl_afu_put() and kfree() again.
Double frees are often exploitable. But it looks to me like this error path is not easily reachable by an attacker. ocxl_file_register_afu() is only called from ocxl_probe(), and we only go to err_unregister if the sysfs or cdev initialisation fails, which should only happen if we hit ENOMEM, or we have a duplicate device which would be a device-tree/hardware error. But maybe Fred can check more closely, I don't know the driver that well. cheers
quoted hunk ↗ jump to hunk
Fix this by adding free_minor() and return to err_unregister error path. Fixes: 75ca758adbaf ("ocxl: Create a clear delineation between ocxl backend & frontend") Signed-off-by: Hangyu Hua <redacted> --- drivers/misc/ocxl/file.c | 2 ++ 1 file changed, 2 insertions(+)diff --git a/drivers/misc/ocxl/file.c b/drivers/misc/ocxl/file.c index d881f5e40ad9..6777c419a8da 100644 --- a/drivers/misc/ocxl/file.c +++ b/drivers/misc/ocxl/file.c@@ -556,7 +556,9 @@ int ocxl_file_register_afu(struct ocxl_afu *afu) err_unregister: ocxl_sysfs_unregister_afu(info); // safe to call even if register failed + free_minor(info); device_unregister(&info->dev); + return rc; err_put: ocxl_afu_put(afu); free_minor(info);-- 2.25.1