linux-kernel - [PATCH] uio: potential double frees if __uio_register

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Date:   Thu, 2 Aug 2018 11:24:47 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Hans J. Koch" <hjk@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] uio: potential double frees if __uio_register_device() fails

The uio_unregister_device() function assumes that if "info->uio_dev" is
non-NULL that means "info" is fully allocated.  Setting info->uio_de
has to be the last thing in the function.

In the current code, if request_threaded_irq() fails then we return with
info->uio_dev set to non-NULL but info is not fully allocated and it can
lead to double frees.

Fixes: beafc54c4e2f ("UIO: Add the User IO core code")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index 144cf7365288..cf388c384553 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -957,8 +957,6 @@ int __uio_register_device(struct module *owner,
 	if (ret)
 		goto err_uio_dev_add_attributes;
 
-	info->uio_dev = idev;
-
 	if (info->irq && (info->irq != UIO_IRQ_CUSTOM)) {
 		/*
 		 * Note that we deliberately don't use devm_request_irq
@@ -975,6 +973,7 @@ int __uio_register_device(struct module *owner,
 			goto err_request_irq;
 	}
 
+	info->uio_dev = idev;
 	return 0;
 
 err_request_irq: