uio: Fix an Oops on load

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>

1 files changed, 5 insertions, 2 deletions

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index 85644669fbe7..0a357db4b31b 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -961,6 +961,8 @@ 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
@@ -972,11 +974,12 @@ 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: