RE: [PATCH] uio: Fix an Oops on load

From: Mathias Thore
Date: Fri Oct 26 2018 - 03:41:48 EST

Thanks for the quick fix. I've tested it and it seems OK.

Tested-by: Mathias Thore <Mathias.Thore@xxxxxxxxxxxx>

-----Original Message-----
From: Dan Carpenter [mailto:dan.carpenter@xxxxxxxxxx]
Sent: Friday, 26 October 2018 09:20
To: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>; Mathias Thore <Mathias.Thore@xxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Subject: [PATCH] uio: Fix an Oops on load

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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>
drivers/uio/uio.c | 7 +++++--
1 file 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;