From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx198.postini.com [74.125.245.198]) by kanga.kvack.org (Postfix) with SMTP id CDDDD6B00A3 for ; Tue, 10 Sep 2013 19:51:05 -0400 (EDT) Message-ID: <1378857061.15187.1.camel@joe-AO722> Subject: Re: slab: krealloc with GFP_ZERO defect From: Joe Perches Date: Tue, 10 Sep 2013 16:51:01 -0700 In-Reply-To: <1377812836.1928.135.camel@joe-AO722> References: <1377812836.1928.135.camel@joe-AO722> Content-Type: text/plain; charset="ISO-8859-1" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: Pekka Enberg , Matt Mackall , linux-mm , LKML ping? On Thu, 2013-08-29 at 14:47 -0700, Joe Perches wrote: > This sequence can return non-zeroed memory from the > padding area of the original allocation. > > ptr = kzalloc(foo, GFP_KERNEL); > if (!ptr) > ... > new_ptr = krealloc(ptr, foo + bar, GFP_KERNEL | __GFP_ZERO); > > If the realloc size is within the first actual allocation > then the additional memory is not zeroed. > > If the realloc size is not within the original allocation > size, any non-zeroed padding from the original allocation > is overwriting newly allocated zeroed memory. > > Maybe someone more familiar with the alignment & padding can > add the proper memset(,0,) for the __GFP_ZERO cases and also > optimize kmalloc_track_caller to not use __GFP_ZERO, memcpy > the current (non padded) size and zero the newly returned > remainder if necessary. > > from: mm/util.c > --------------------------- > static __always_inline void *__do_krealloc(const void *p, size_t new_size, > gfp_t flags) > { > void *ret; > size_t ks = 0; > > if (p) > ks = ksize(p); > > if (ks >= new_size) > return (void *)p; > > ret = kmalloc_track_caller(new_size, flags); > if (ret && p) > memcpy(ret, p, ks); > > return ret; > } > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org