[PATCH] IB/qib: Validate ->show()/store() callbacks before calling them

[PATCH] IB/qib: Validate ->show()/store() callbacks before calling them

[Viresh Kumar]

The permissions of the read-only or write-only sysfs files can be
changed (as root) and the user can then try to read a write-only file or
write to a read-only file which will lead to kernel crash here.

Protect against that by always validating the show/store callbacks.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 drivers/infiniband/hw/qib/qib_sysfs.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/infiniband/hw/qib/qib_sysfs.c b/drivers/infiniband/hw/qib/qib_sysfs.c
index 3926be78036e..568b21eb6ea1 100644
--- a/drivers/infiniband/hw/qib/qib_sysfs.c
+++ b/drivers/infiniband/hw/qib/qib_sysfs.c
@@ -301,6 +301,9 @@ static ssize_t qib_portattr_show(struct kobject *kobj,
 	struct qib_pportdata *ppd =
 		container_of(kobj, struct qib_pportdata, pport_kobj);
 
+	if (!pattr->show)
+		return -EIO;
+
 	return pattr->show(ppd, buf);
 }
 
@@ -312,6 +315,9 @@ static ssize_t qib_portattr_store(struct kobject *kobj,
 	struct qib_pportdata *ppd =
 		container_of(kobj, struct qib_pportdata, pport_kobj);
 
+	if (!pattr->store)
+		return -EIO;
+
 	return pattr->store(ppd, buf, len);
 }
 
-- 
2.21.0.rc0.269.g1a574e7a288b

Re: [PATCH] IB/qib: Validate ->show()/store() callbacks before calling them

[Greg Kroah-Hartman]

On Thu, Nov 07, 2019 at 08:50:25AM +0530, Viresh Kumar wrote:
> The permissions of the read-only or write-only sysfs files can be
> changed (as root) and the user can then try to read a write-only file or
> write to a read-only file which will lead to kernel crash here.
> 
> Protect against that by always validating the show/store callbacks.
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
>  drivers/infiniband/hw/qib/qib_sysfs.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Re: [PATCH] IB/qib: Validate ->show()/store() callbacks before calling them

[Jason Gunthorpe]

On Thu, Nov 07, 2019 at 08:50:25AM +0530, Viresh Kumar wrote:
> The permissions of the read-only or write-only sysfs files can be
> changed (as root) and the user can then try to read a write-only file or
> write to a read-only file which will lead to kernel crash here.
> 
> Protect against that by always validating the show/store callbacks.
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
>  drivers/infiniband/hw/qib/qib_sysfs.c | 6 ++++++
>  1 file changed, 6 insertions(+)

Applied to for-next, thanks

Jason