uio: Fix an Oops on load

commit 432798195bbce1f8cd33d1c0284d0538835e25fb upstream.

I was trying to solve a double free but I introduced a more serious
NULL dereference bug.  The problem is that if there is an IRQ which
triggers immediately, then we need "info->uio_dev" but it's not set yet.

This patch puts the original initialization back to how it was and just
sets info->uio_dev to NULL on the error path so it should solve both
the Oops and the double free.

Fixes: f019f07ecf6a ("uio: potential double frees if __uio_register_device() fails")
Reported-by: Mathias Thore <Mathias.Thore@infinera.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable <stable@vger.kernel.org>
Tested-by: Mathias Thore <Mathias.Thore@infinera.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index 0ab15d8..50fe1f7 100644 (file)
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -842,6 +842,8 @@ 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
@@ -853,11 +855,12 @@ int __uio_register_device(struct module *owner,
                 */
                ret = request_irq(info->irq, uio_interrupt,
                                  info->irq_flags, info->name, idev);
-               if (ret)
+               if (ret) {
+                       info->uio_dev = NULL;
                        goto err_request_irq;
+               }
        }
 
-       info->uio_dev = idev;
        return 0;
 
 err_request_irq: