[PATCH 3.18 16/24] uio: Fix an Oops on load

From: Greg Kroah-Hartman
Date: Mon Nov 26 2018 - 05:53:00 EST

3.18-stable review patch. If anyone has any objections, please let me know.


From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

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@xxxxxxxxxxxx>
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Tested-by: Mathias Thore <Mathias.Thore@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/uio/uio.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -841,14 +841,17 @@ int __uio_register_device(struct module
if (ret)
goto err_uio_dev_add_attributes;

+ info->uio_dev = idev;
if (info->irq && (info->irq != UIO_IRQ_CUSTOM)) {
ret = devm_request_irq(idev->dev, 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;