Re: [PATCH] USB: gadget: g_fs: possible invalid pointer referencebug fixed

From: Sergei Shtylyov
Date: Tue Jun 15 2010 - 06:17:55 EST


Michal Nazarewicz wrote:

During __gfs_do_config() some invalid pointers may be left
in usb_configuration::interfaces array from previous calls
to the __gfs_do_config() for the same configuration. This
will always happen if an user space function which has
a fewer then the last user space function registers itself.
Composite's set_config() function that a pointer after the
last interface in usb_configuration::interface is NULL
unless the array is full.

This patch makes the __gfs_do_config() make sure that if the
usb_configuration::interface is not full then a pointer
after the last interface is NULL.

Signed-off-by: Michal Nazarewicz <m.nazarewicz@xxxxxxxxxxx>
Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
drivers/usb/gadget/g_ffs.c | 11 +++++++++++
1 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/drivers/usb/gadget/g_ffs.c b/drivers/usb/gadget/g_ffs.c
index 2f26470..da3a9e4 100644
--- a/drivers/usb/gadget/g_ffs.c
+++ b/drivers/usb/gadget/g_ffs.c
@@ -392,6 +392,17 @@ static int __gfs_do_config(struct usb_configuration *c,
if (unlikely(ret < 0))
return ret;
+ /* After previous do_configs there may be some invalid
+ * pointers in c->interface array. This happens every time
+ * a user space function with fewer interfaces than a user
+ * space function that was run before the new one is run. The
+ * compasit's set_config() assumes that if there is no more
+ * then MAX_CONFIG_INTERFACES interfaces in a configuration
+ * then there is a NULL pointer after the last interface in
+ * c->interface array. We need to make sure this is true. */

According to CodingStyle, the preferred style of the multi-line comments is this:

* bla
* bla

+ if (c->next_interface_id < ARRAY_SIZE(c->interface))
+ c->interface[c->next_interface_id] = NULL;
return 0;

WBR, Sergei

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