From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anderson Briglia Subject: Re: [patch 3/5] Add MMC password protection (lock/unlock) support V3 Date: Tue, 10 Jan 2006 17:45:36 -0400 Message-ID: <43C42B00.60206@indt.org.br> References: <43C2E0A2.3090701@indt.org.br> <20060109224204.GH19131@flint.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20060109224204.GH19131@flint.arm.linux.org.uk> Sender: linux-kernel-owner@vger.kernel.org To: Russell King Cc: linux-kernel@vger.kernel.org, "Linux-omap-open-source@linux.omap.com" , linux@arm.linux.org.uk, ext David Brownell , Tony Lindgren , drzeus-list@drzeus.cx, "Aguiar Carlos (EXT-INdT/Manaus)" , "Lizardo Anderson (EXT-INdT/Manaus)" List-Id: linux-omap@vger.kernel.org Russell King wrote: >On Mon, Jan 09, 2006 at 06:16:02PM -0400, Anderson Briglia wrote: > > >>+ dev = bus_find_device(&mmc_bus_type, NULL, NULL, mmc_match_lockable); >>+ if (!dev) >>+ goto error; >>+ card = dev_to_mmc_card(dev); >>+ >>+ if (operation == KEY_OP_INSTANTIATE) { /* KEY_OP_INSTANTIATE */ >>+ if (mmc_card_locked(card)) { >>+ ret = mmc_lock_unlock(card, key, MMC_LOCK_MODE_UNLOCK); >>+ mmc_remove_card(card); >>+ mmc_register_card(card); >>+ } >>+ else >>+ ret = mmc_lock_unlock(card, key, MMC_LOCK_MODE_SET_PWD); >> >> > >I really don't like this - if the MMC card is not locked, we set a >password on it. If it's locked, we unlock it. > >That's a potential race condition if you're trying to unlock a card >and the card is changed beneath you while you slept waiting for >memory - you end up setting that password on the new card. > >It's far better to have separate "unlock this card" and "set a >password on this card" commands rather than trying to combine the >two operations. > > Ok. >Also, removing and re-registering a card is an offence. These >things are ref-counted, and mmc_remove_card() will drop the last >reference - so the memory associated with it will be freed. Then >you re-register it. Whoops. > >If you merely want to try to attach a driver, use device_attach() >instead. > > If we use device_attach(), the mmc_block driver is not informed about the card's unlocking. I did some tests, using device_attach() instead of those mmc functions and seems that the mmc_block driver tries to use a invalid device reference. What do you suggest on this case? >Also, what if you have multiple MMC cards? I have a board here >with two MMC slots. I'd rather not have it try to set the same >password on both devices. > > Sorry, but this series of patches only support one mmc host. I'll update the TODO section of the summary e-mail. Anderson Briglia INdT - Manaus