Hi, On 10 October 2017 at 13:14, Bin Liu <b-liu@xxxxxx> wrote: > On Tue, Oct 10, 2017 at 08:17:34AM +1100, Jonathan Liu wrote: >> Hi, >> >> On 10 October 2017 at 01:23, Bin Liu <b-liu@xxxxxx> wrote: >> > Hi, >> > >> > On Tue, Sep 26, 2017 at 09:39:23PM +1000, Jonathan Liu wrote: >> >> This fixes a kernel oops when unloading the driver due to usb_put_phy >> >> being called after usb_phy_generic_unregister when the device is >> >> detached. Calling usb_phy_generic_unregister causes x->dev->driver to >> >> be NULL in usb_put_phy and results in a NULL pointer dereference. >> >> >> >> As we are now explicitly managing the lifetime of usb_phy, >> >> devm_usb_get_phy is changed to usb_get_phy and we call usb_put_phy in >> >> the probe error path. >> >> >> >> Cc: stable@xxxxxxxxxxxxxxx # v4.3+ >> >> Signed-off-by: Jonathan Liu <net147@xxxxxxxxx> >> >> --- >> >> drivers/usb/musb/sunxi.c | 8 ++++++-- >> >> 1 file changed, 6 insertions(+), 2 deletions(-) >> >> >> >> diff --git a/drivers/usb/musb/sunxi.c b/drivers/usb/musb/sunxi.c >> >> index c9a09b5bb6e5..8eed61042103 100644 >> >> --- a/drivers/usb/musb/sunxi.c >> >> +++ b/drivers/usb/musb/sunxi.c >> >> @@ -297,6 +297,8 @@ static int sunxi_musb_exit(struct musb *musb) >> >> if (test_bit(SUNXI_MUSB_FL_HAS_SRAM, &glue->flags)) >> >> sunxi_sram_release(musb->controller->parent); >> >> >> >> + usb_put_phy(glue->xceiv); >> > >> > Will devm_usb_put_phy() solve the issue too? Then you don't need the >> > changes in sunxi_musb_probe() below. >> > >> >> devm_usb_put_phy does solve the issue without changes in >> sunxi_musb_probe but I think it is clearer that the lifetime is >> explicitly managed if we don't mix implicit and explicit freeing of >> resources. > > Then what is the purpose of the devm_* API? > > The original bug was that devm_usb_get_phy() is called in _probe, but > devm_usb_put_phy() was never called, which caused the device ref count > unbalanced. It is not related to implicit/explicit resource management. > > devm_* is recommended whenever applicable. > Ok. Will use devm_usb_put_phy in v2 patch. > Regards, > -Bin. > Regards, Jonathan -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
