Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754323Ab2ENDYB (ORCPT ); Sun, 13 May 2012 23:24:01 -0400 Received: from mail-gg0-f174.google.com ([209.85.161.174]:47303 "EHLO mail-gg0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753179Ab2ENDX7 convert rfc822-to-8bit (ORCPT ); Sun, 13 May 2012 23:23:59 -0400 MIME-Version: 1.0 In-Reply-To: <20120512001717.GB14782@lizard> References: <20120512001506.GA8653@lizard> <20120512001717.GB14782@lizard> Date: Sun, 13 May 2012 20:23:58 -0700 X-Google-Sender-Auth: bKZDykDN_-wAzQqkbhOJg9j0mUY Message-ID: Subject: Re: [PATCH 02/11] persistent_ram: Fix buffer size clamping during writes From: Colin Cross To: Anton Vorontsov Cc: Greg Kroah-Hartman , Kees Cook , Arnd Bergmann , John Stultz , arve@android.com, Rebecca Schultz Zavin , Jesper Juhl , Randy Dunlap , Stephen Boyd , Thomas Meyer , Andrew Morton , Marco Stornelli , WANG Cong , linux-kernel@vger.kernel.org, devel@driverdev.osuosl.org, linaro-kernel@lists.linaro.org, patches@linaro.org, kernel-team@android.com Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2557 Lines: 70 On Fri, May 11, 2012 at 5:17 PM, Anton Vorontsov wrote: > This is a longstanding bug, almost unnoticeable when calling > persistent_ram_write() for small buffers. > > But when called for large data buffers, the write routine behaves > incorrectly, as the size may never update: instead of clamping > the size to the maximum buffer size, buffer_size_add_clamp() returns > an error (which is never checked by the write routine, btw). > > To fix this, we now use buffer_size_add() that actually clamps the > size to the max value. > > Also remove buffer_size_add_clamp(), it is no longer needed. > > Signed-off-by: Anton Vorontsov > --- > ?drivers/staging/android/persistent_ram.c | ? 19 +------------------ > ?1 file changed, 1 insertion(+), 18 deletions(-) > > diff --git a/drivers/staging/android/persistent_ram.c b/drivers/staging/android/persistent_ram.c > index 12444fd..13a12bc 100644 > --- a/drivers/staging/android/persistent_ram.c > +++ b/drivers/staging/android/persistent_ram.c > @@ -79,23 +79,6 @@ static inline void buffer_size_add(struct persistent_ram_zone *prz, size_t a) > ? ? ? ?} while (atomic_cmpxchg(&prz->buffer->size, old, new) != old); > ?} > > -/* increase the size counter, retuning an error if it hits the max size */ > -static inline ssize_t buffer_size_add_clamp(struct persistent_ram_zone *prz, > - ? ? ? size_t a) > -{ > - ? ? ? size_t old; > - ? ? ? size_t new; > - > - ? ? ? do { > - ? ? ? ? ? ? ? old = atomic_read(&prz->buffer->size); > - ? ? ? ? ? ? ? new = old + a; > - ? ? ? ? ? ? ? if (new > prz->buffer_size) > - ? ? ? ? ? ? ? ? ? ? ? return -ENOMEM; > - ? ? ? } while (atomic_cmpxchg(&prz->buffer->size, old, new) != old); > - > - ? ? ? return 0; > -} > - > ?static void notrace persistent_ram_encode_rs8(struct persistent_ram_zone *prz, > ? ? ? ?uint8_t *data, size_t len, uint8_t *ecc) > ?{ > @@ -300,7 +283,7 @@ int notrace persistent_ram_write(struct persistent_ram_zone *prz, > ? ? ? ? ? ? ? ?c = prz->buffer_size; > ? ? ? ?} > > - ? ? ? buffer_size_add_clamp(prz, c); > + ? ? ? buffer_size_add(prz, c); > > ? ? ? ?start = buffer_start_add(prz, c); > > -- > 1.7.9.2 > Acked-by: Colin Cross This is a bug fix for a bug introduced in 3.4-rc1, it should go into 3.4 if there is another rc. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/