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Subject[PATCH] Net, USB, Option, hso: Do not dereference NULL pointer
In drivers/net/usb/hso.c::hso_create_bulk_serial_device() we have this 
code:
...
serial = kzalloc(sizeof(*serial), GFP_KERNEL);
if (!serial)
goto exit;
...
exit:
hso_free_tiomget(serial);
...
hso_free_tiomget() directly dereferences its argument, which in the
example above is a NULL pointer, ouch.
I could just add a 'if (serial)' test at the 'exit' label, but since most
freeing functions in the kernel accept NULL pointers (and it seems like
this was also assumed here) I opted to instead change 'hso_free_tiomget()'
so that it is safe to call it with a NULL argument. I also modified the
function to get rid of a pointles conditional before the call to
'usb_free_urb()' since that function already tests for NULL itself -
besides fixing the NULL deref this change also buys us a few bytes in
size.
Before:
$ size drivers/net/usb/hso.o
text data bss dec hex filename
32200 592 9960 42752 a700 drivers/net/usb/hso.o
After:
$ size drivers/net/usb/hso.o
text data bss dec hex filename
32196 592 9960 42748 a6fc drivers/net/usb/hso.o

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
---
hso.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
index bed8fce..6d83812 100644
--- a/drivers/net/usb/hso.c
+++ b/drivers/net/usb/hso.c
@@ -2628,15 +2628,15 @@ exit:

static void hso_free_tiomget(struct hso_serial *serial)
{
- struct hso_tiocmget *tiocmget = serial->tiocmget;
+ struct hso_tiocmget *tiocmget;
+ if (!serial)
+ return;
+ tiocmget = serial->tiocmget;
if (tiocmget) {
- if (tiocmget->urb) {
- usb_free_urb(tiocmget->urb);
- tiocmget->urb = NULL;
- }
+ usb_free_urb(tiocmget->urb);
+ tiocmget->urb = NULL;
serial->tiocmget = NULL;
kfree(tiocmget);
-
}
}


--
Jesper Juhl <jj@chaosbits.net> http://www.chaosbits.net/
Plain text mails only, please.
Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html



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