From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx101.postini.com [74.125.245.101]) by kanga.kvack.org (Postfix) with SMTP id 0908E6B0062 for ; Tue, 5 Jun 2012 18:56:02 -0400 (EDT) Date: Tue, 5 Jun 2012 15:56:01 -0700 From: Andrew Morton Subject: Re: [PATCH] mm: Make vb_alloc() more foolproof Message-Id: <20120605155601.738bde7c.akpm@linux-foundation.org> In-Reply-To: <1338936056-4092-1-git-send-email-jack@suse.cz> References: <1338936056-4092-1-git-send-email-jack@suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Jan Kara Cc: linux-mm@kvack.org On Wed, 6 Jun 2012 00:40:56 +0200 Jan Kara wrote: > If someone calls vb_alloc() (or vm_map_ram() for that matter) to allocate > 0 bytes (0 pages), get_order() returns BITS_PER_LONG - PAGE_CACHE_SHIFT > and interesting stuff happens. So make debugging such problems easier and > warn about 0-size allocation. > > Signed-off-by: Jan Kara > --- > mm/vmalloc.c | 9 +++++++++ > 1 files changed, 9 insertions(+), 0 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 2aad499..bebee70 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -904,6 +904,15 @@ static void *vb_alloc(unsigned long size, gfp_t gfp_mask) > > BUG_ON(size & ~PAGE_MASK); > BUG_ON(size > PAGE_SIZE*VMAP_MAX_ALLOC); > + if (size == 0) { > + /* > + * Allocating 0 bytes isn't what caller wants since > + * get_order(0) returns funny result. Just warn and terminate > + * early. > + */ > + WARN_ON(1); > + return NULL; > + } > order = get_order(size); Spose so. You got bitten, I assume ;) We can neaten the implementation: --- a/mm/vmalloc.c~mm-make-vb_alloc-more-foolproof-fix +++ a/mm/vmalloc.c @@ -904,13 +904,12 @@ static void *vb_alloc(unsigned long size BUG_ON(size & ~PAGE_MASK); BUG_ON(size > PAGE_SIZE*VMAP_MAX_ALLOC); - if (size == 0) { + if (WARN_ON(size == 0)) { /* * Allocating 0 bytes isn't what caller wants since * get_order(0) returns funny result. Just warn and terminate * early. */ - WARN_ON(1); return NULL; } order = get_order(size); and that gives us the unlikely() hit too. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org