| Message ID | Y3uOxcvowFq75Tzv@kili (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | usb: gadget: function: use after free in printer_close() | expand |
Hi Dan, I'm fine with either symmetrically removing the DBG() from "printer_open()" or with this version of the patch. It seems to me that this version better fits "fixing UAF", though. Whether the driver is too verbose is another matter, and if it is, it deserves its own patch because DBG() invocations are sprinkled here and there. W dniu 21.11.2022 o 15:44, Dan Carpenter pisze: > The printer_dev_free() function frees "dev" but then it is dereferenced > by the debug code on the next line. Flip the order to avoid the use after > free. > > Fixes: e8d5f92b8d30 ("usb: gadget: function: printer: fix use-after-free in __lock_acquire") > Signed-off-by: Dan Carpenter <error27@gmail.com> Acked-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com> > --- > v2: In the v1, I just deleted the printk but Andrzej thought it was > worth preserving. > > drivers/usb/gadget/function/f_printer.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c > index a881c69b1f2b..01e842e1ba2f 100644 > --- a/drivers/usb/gadget/function/f_printer.c > +++ b/drivers/usb/gadget/function/f_printer.c > @@ -381,8 +381,8 @@ printer_close(struct inode *inode, struct file *fd) > dev->printer_status &= ~PRINTER_SELECTED; > spin_unlock_irqrestore(&dev->lock, flags); > > - kref_put(&dev->kref, printer_dev_free); > DBG(dev, "printer_close\n"); > + kref_put(&dev->kref, printer_dev_free); > > return 0; > }
On Mon, Nov 21, 2022 at 04:32:52PM +0100, Andrzej Pietrasiewicz wrote: > Hi Dan, > > I'm fine with either symmetrically removing the DBG() from "printer_open()" > or with this version of the patch. > > It seems to me that this version better fits "fixing UAF", though. > Whether the driver is too verbose is another matter, and if it is, > it deserves its own patch because DBG() invocations are sprinkled > here and there. It is too verbose, but I'm trying to cut my kernel work to an hour a day and then all day Friday so I don't have time to clean to do clean up work. A UAF is sort of high value but clean up is endless. I obviously considered this as v1 but thought deleting was better. I still do. :) But it's not worth spending time on. > > W dniu 21.11.2022 o 15:44, Dan Carpenter pisze: > > The printer_dev_free() function frees "dev" but then it is dereferenced > > by the debug code on the next line. Flip the order to avoid the use after > > free. > > > > Fixes: e8d5f92b8d30 ("usb: gadget: function: printer: fix use-after-free in __lock_acquire") > > Signed-off-by: Dan Carpenter <error27@gmail.com> > > Acked-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com> Thanks! regards, dan carpenter
Hi Dan, W dniu 22.11.2022 o 08:00, Dan Carpenter pisze: > On Mon, Nov 21, 2022 at 04:32:52PM +0100, Andrzej Pietrasiewicz wrote: >> Hi Dan, >> >> I'm fine with either symmetrically removing the DBG() from "printer_open()" >> or with this version of the patch. >> >> It seems to me that this version better fits "fixing UAF", though. >> Whether the driver is too verbose is another matter, and if it is, >> it deserves its own patch because DBG() invocations are sprinkled >> here and there. > > It is too verbose, but I'm trying to cut my kernel work to an hour a day > and then all day Friday so I don't have time to clean to do clean up > work. A UAF is sort of high value but clean up is endless. > I volunteer to reduce the amount of debug messages it produces. Andrzej > I obviously considered this as v1 but thought deleting was better. I > still do. :) But it's not worth spending time on. > >> >> W dniu 21.11.2022 o 15:44, Dan Carpenter pisze: >>> The printer_dev_free() function frees "dev" but then it is dereferenced >>> by the debug code on the next line. Flip the order to avoid the use after >>> free. >>> >>> Fixes: e8d5f92b8d30 ("usb: gadget: function: printer: fix use-after-free in __lock_acquire") >>> Signed-off-by: Dan Carpenter <error27@gmail.com> >> >> Acked-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com> > > Thanks! > > regards, > dan carpenter >
diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c index a881c69b1f2b..01e842e1ba2f 100644 --- a/drivers/usb/gadget/function/f_printer.c +++ b/drivers/usb/gadget/function/f_printer.c @@ -381,8 +381,8 @@ printer_close(struct inode *inode, struct file *fd) dev->printer_status &= ~PRINTER_SELECTED; spin_unlock_irqrestore(&dev->lock, flags); - kref_put(&dev->kref, printer_dev_free); DBG(dev, "printer_close\n"); + kref_put(&dev->kref, printer_dev_free); return 0; }
The printer_dev_free() function frees "dev" but then it is dereferenced by the debug code on the next line. Flip the order to avoid the use after free. Fixes: e8d5f92b8d30 ("usb: gadget: function: printer: fix use-after-free in __lock_acquire") Signed-off-by: Dan Carpenter <error27@gmail.com> --- v2: In the v1, I just deleted the printk but Andrzej thought it was worth preserving. drivers/usb/gadget/function/f_printer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)