From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3A21BC83F2F for ; Thu, 31 Aug 2023 19:48:01 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 214FC8D001E; Thu, 31 Aug 2023 15:48:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1C4D08D0002; Thu, 31 Aug 2023 15:48:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 08D878D001E; Thu, 31 Aug 2023 15:48:00 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id ED2B18D0002 for ; Thu, 31 Aug 2023 15:47:59 -0400 (EDT) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id C29B680407 for ; Thu, 31 Aug 2023 19:47:59 +0000 (UTC) X-FDA: 81185435478.08.E2D610C Received: from mail-lf1-f41.google.com (mail-lf1-f41.google.com [209.85.167.41]) by imf29.hostedemail.com (Postfix) with ESMTP id BD8D0120025 for ; Thu, 31 Aug 2023 19:47:56 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=gmail.com header.s=20221208 header.b=AC2VGGO7; spf=pass (imf29.hostedemail.com: domain of urezki@gmail.com designates 209.85.167.41 as permitted sender) smtp.mailfrom=urezki@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1693511276; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=SP7TySB2lx9oeTcWR9xzk9DZs28Uo52pxRwlR9h0oYE=; b=3ncF3z7WrOryZ6eapaouuDv7UjBi4pigYvJ4U1XBQ5p4Qb464Sbworjsk/hMU0E+jEwWV6 aaa27elZu0eBkBFqGwBeVSRWUZ6nXyT2mue9j4IbX0aItbTnul4OlkF+YfMNF2RqQOCXzw rbar56k/1g2yIuQVuFwyBAYdDCRsCKs= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=gmail.com header.s=20221208 header.b=AC2VGGO7; spf=pass (imf29.hostedemail.com: domain of urezki@gmail.com designates 209.85.167.41 as permitted sender) smtp.mailfrom=urezki@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1693511276; a=rsa-sha256; cv=none; b=U6z0dqzItkt7QJb19kGCu6N58lfN9VUMQbYAUaemKnPPm3jxpVUQ2AhAjRz1P4TO2VQQpD RmkeXO3qh+ptTSh/HvkUC9EZ3WU6NFMXZPDYUzbuznxzVrZVIjaX4Syow/As+VF4jKj+/2 r/2v0TbvwJvAFL2DjEipiEjC0kob10A= Received: by mail-lf1-f41.google.com with SMTP id 2adb3069b0e04-50098cc8967so2160884e87.1 for ; Thu, 31 Aug 2023 12:47:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1693511275; x=1694116075; darn=kvack.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:from:to:cc:subject:date:message-id:reply-to; bh=SP7TySB2lx9oeTcWR9xzk9DZs28Uo52pxRwlR9h0oYE=; b=AC2VGGO7JszS06Lj0tJznAP2LC9JuV/YMbB7FozBPbiu58KUz6X+dzifPoSpywCfi1 tEZpJGw64v52i4Q7b8A3hC4tipVVHtv8W1XYD77em0mdUiyRCz1HHFpQbtKVbEX67QA9 Zk5ckVHpoHNe8VKjfgfSidzyxnrcFe+NhPtGTyxAaC43v3qoHHFR3JyAJ/1SLsiSut7s bylypygPG5gkRa2X5so+f8tHQZln/2CnTc9LdkZGI2q+nAuaHUyI9206nzu9iVDW4Tvj oBNMd1J6mV/ZN0L64RS//+8YqtpY8w8MN6zmqtgfMwc6hzCak9xhXeFjN8vDMxMQWbFZ 1Fpg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1693511275; x=1694116075; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=SP7TySB2lx9oeTcWR9xzk9DZs28Uo52pxRwlR9h0oYE=; b=OfBeOndCvvFWLGGMs3ykuQuxd5GqFNQ3YVywJk6vo9Fl+PXIeZAK5APC7v/mzxzObg tXbeKYLuZX3vq7ckBOvWr8KEJ2y+0y8E3TocnWyM/fBpLW0sb8zf2crJmX2cTcu/8ilM hiKysAmlllDAlEGO6eJs7wkjXpHjh1NMgdSk56Ms2N4HOjJi7hzcC6UFXS95Gv+pzTQk Nt1EKXXccPuplwllkjAEiwSiKxGpbzrVRWhM4uTLqPQz+AhtL8SiXn48Xi6P7FVH6E14 7ieuINFdiiGdI1k2s/war+gVrw+QixjMS34B4T97baGOlvUlpzCMVHbN1Busn68G6zjt KJ6w== X-Gm-Message-State: AOJu0YzfBUhuhdrtjfWfO0rStNsWJvXxJxHIaUneHvQ0DjwPFSAgYpYd 7S28O+GGwx7Mv4s0xNmEuOw= X-Google-Smtp-Source: AGHT+IFEJkN5eVx2umhjiyHxQLqR70bhX744axFi5IzfUINZasMrBF4W8Gt6ZSafIP6tcdqLKEDfrg== X-Received: by 2002:a05:6512:3994:b0:500:b64f:afbe with SMTP id j20-20020a056512399400b00500b64fafbemr226655lfu.19.1693511274531; Thu, 31 Aug 2023 12:47:54 -0700 (PDT) Received: from pc636 ([155.137.26.201]) by smtp.gmail.com with ESMTPSA id t6-20020a19ad06000000b004fe2e94f8fdsm386459lfc.236.2023.08.31.12.47.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 31 Aug 2023 12:47:54 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Thu, 31 Aug 2023 21:47:52 +0200 To: "Joel Fernandes (Google)" Cc: linux-kernel@vger.kernel.org, Andrew Morton , Uladzislau Rezki , Christoph Hellwig , Lorenzo Stoakes , Zhen Lei , "Paul E . McKenney" , rcu@vger.kernel.org, Zqiang , Matthew Wilcox , linux-mm@kvack.org Subject: Re: [PATCH v2 1/2] mm/vmalloc: Add a safer version of find_vm_area() for debug Message-ID: References: <20230831171827.2625016-1-joel@joelfernandes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230831171827.2625016-1-joel@joelfernandes.org> X-Rspamd-Queue-Id: BD8D0120025 X-Rspam-User: X-Stat-Signature: s77yjicrb49s63dyhbbg4tib8whtz431 X-Rspamd-Server: rspam01 X-HE-Tag: 1693511276-156668 X-HE-Meta: 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 MklCxyMv 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Aug 31, 2023 at 05:18:25PM +0000, Joel Fernandes (Google) wrote: > It is unsafe to dump vmalloc area information when trying to do so from > some contexts. Add a safer trylock version of the same function to do a > best-effort VMA finding and use it from vmalloc_dump_obj(). > > [apply test robot feedback on unused function fix.] > > Reported-by: Zhen Lei > Cc: Paul E. McKenney > Cc: rcu@vger.kernel.org > Cc: Zqiang > Reviewed-by: Matthew Wilcox (Oracle) > Signed-off-by: Joel Fernandes (Google) > --- > v1->v2: Apply review tags and test robot feedback. > > mm/vmalloc.c | 39 ++++++++++++++++++++++++++++++++++++++- > 1 file changed, 38 insertions(+), 1 deletion(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 93cf99aba335..f09e882ae3b8 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -1865,6 +1865,20 @@ struct vmap_area *find_vmap_area(unsigned long addr) > return va; > } > > +#ifdef CONFIG_PRINTK > +static struct vmap_area *find_vmap_area_trylock(unsigned long addr) > +{ > + struct vmap_area *va; > + > + if (!spin_trylock(&vmap_area_lock)) > + return NULL; > + va = __find_vmap_area(addr, &vmap_area_root); > + spin_unlock(&vmap_area_lock); > + > + return va; > +} > +#endif > + > static struct vmap_area *find_unlink_vmap_area(unsigned long addr) > { > struct vmap_area *va; > @@ -2671,6 +2685,29 @@ struct vm_struct *find_vm_area(const void *addr) > return va->vm; > } > > +/** > + * try_to_find_vm_area - find a continuous kernel virtual area > + * @addr: base address > + * > + * This function is the same as find_vm_area() except that it is > + * safe to call if vmap_area_lock is already held and returns NULL > + * if it is. See comments in find_vmap_area() for other details. > + * > + * Return: the area descriptor on success or %NULL on failure. > + */ > +#ifdef CONFIG_PRINTK > +static struct vm_struct *try_to_find_vm_area(const void *addr) > +{ > + struct vmap_area *va; > + > + va = find_vmap_area_trylock((unsigned long)addr); > + if (!va) > + return NULL; > + > + return va->vm; > +} > +#endif > + > /** > * remove_vm_area - find and remove a continuous kernel virtual area > * @addr: base address > @@ -4277,7 +4314,7 @@ bool vmalloc_dump_obj(void *object) > struct vm_struct *vm; > void *objp = (void *)PAGE_ALIGN((unsigned long)object); > > - vm = find_vm_area(objp); > + vm = try_to_find_vm_area(objp); > if (!vm) > return false; > pr_cont(" %u-page vmalloc region starting at %#lx allocated at %pS\n", > I am not sure if this patch makes a lot of sense. I agree, this is a problem and it mitigates it. But it is broken in terms of once you drop the lock, the VA should not be accessed. Is that a real issue or it gets triggered due to some syntetic test case? If i were you, i would go with open-coded version of trylock. Because there is only one user so far. -- Uladzislau Rezki