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 260CDC32793 for ; Wed, 18 Jan 2023 18:06:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A1DB86B0072; Wed, 18 Jan 2023 13:06:52 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9CDC46B0075; Wed, 18 Jan 2023 13:06:52 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 86E8A6B007B; Wed, 18 Jan 2023 13:06:52 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 778756B0072 for ; Wed, 18 Jan 2023 13:06:52 -0500 (EST) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 3829F140C15 for ; Wed, 18 Jan 2023 18:06:52 +0000 (UTC) X-FDA: 80368700664.19.F6E7AF2 Received: from mail-yw1-f179.google.com (mail-yw1-f179.google.com [209.85.128.179]) by imf26.hostedemail.com (Postfix) with ESMTP id 46456140011 for ; Wed, 18 Jan 2023 18:06:50 +0000 (UTC) Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=JiA4PBg0; spf=pass (imf26.hostedemail.com: domain of surenb@google.com designates 209.85.128.179 as permitted sender) smtp.mailfrom=surenb@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1674065210; 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=DP2jTh2XCGgairHOGKy1hg7eoz80OguUV+dRLV5vdAs=; b=ruiRKOWxbDKPCsC/NcIGocxor4f1tQg8Xrc4d5kY6zq2ajcpEtgw3WQkMevx/nctX2MTOb oKW70H3i97lxPEJM+/G8nRCVZ6QZMnDxOHtwlirvfDP3MpyD2ESUChI2DXWVb9TtTfzTeT YQWwiK3rpJXlbAR1FEoo34qn285OSjg= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=JiA4PBg0; spf=pass (imf26.hostedemail.com: domain of surenb@google.com designates 209.85.128.179 as permitted sender) smtp.mailfrom=surenb@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1674065210; a=rsa-sha256; cv=none; b=ajYuYliQPcQvFPbfEpkvKHJftXbe8JtIFy6nE9Y8E8hV5WnE75k3tx+2xjkqfqnGmfANU1 fpQJNEVmwNIY/dM97wFGmAr9TeyTbEPYyNaFsmwZRZDA8jYcRSyne56nalh0c7F1Xpvps/ 7+urf810K1t0cLNd/00D0ljn2ncuIFI= Received: by mail-yw1-f179.google.com with SMTP id 00721157ae682-4e9adf3673aso143249977b3.10 for ; Wed, 18 Jan 2023 10:06:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=DP2jTh2XCGgairHOGKy1hg7eoz80OguUV+dRLV5vdAs=; b=JiA4PBg0EH7+0/76J3FenR1bnlSGaQgdYOG4b+AglPSOYgfmCcBfM2ErnvDHL4NFM3 xzqZTQIqEjQ7PPX+1LzBhtUDNEk3yB9vFIDmaQSEgWuFp+80LEAWhkoKhNjeIyguxfi9 IcVLilDvjfgehE8DgUarM2edSxsBEPquLtlfDaMXkql9MVVejNVEQ1MrjYhWtOtK9eyN NSxlm5igyPDlNkDxm+4IwWYaT5nE1kzWmkwzXV4INsZk1EToceOcNYpFDzz/xRE0hSNF M6yMgEvu9cHqWkl44Z252S3wbtzdKexOyOHGlp1AVXAzplYZutMDn1Cqdg5ZcfOCxrOc +ReA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=DP2jTh2XCGgairHOGKy1hg7eoz80OguUV+dRLV5vdAs=; b=4wuAc1KuqioVyQFzggHyLTlaGUszi1kJNoXM4anjLtsDKdLIdgQeLhzdCNC/4bOKHV RoK+IwYh5XtaHyZ6oOdOVmFEUPRqeebSLjqrUt/sJ+kxKLPqllddnrWlsJ5D/6AD7JxO Cx3+UYv+L+9PEGWqdlYOAbdPoK9FSaKYNR39Qb/pwC3NtGJvMqvcpTJM48NE5sW4sBYu GnF7bgQxzS0rk4Y95iOymqL8B3P6EJYSDwbh2PpHpMWMrH6jG6hE8244vHU3mIAu9MWr V8dxzEBAvmZ3jOTnUt2bMdHsWt6IIZeDsXb9r3S7A5rCM736ItSggFwGyvGJVS/dLn0R SmSQ== X-Gm-Message-State: AFqh2ko/SOMmFCp+ugSR/QkQpivROf3i9ot/eCrRbgX7ltnCvtTig6iy 3at0DdqouEOFuCNnb7r0M5ln6+R20vwk8pR7Knfv7A== X-Google-Smtp-Source: AMrXdXsZwoic0rKFMDYo0tkFJ6J1kb0TvUIjw3JJelHbDs2OjFUo53z0pnyKmSUsdBlmQsDCtwccF60TcE0BtbKLEzo= X-Received: by 2002:a0d:d484:0:b0:4dc:4113:f224 with SMTP id w126-20020a0dd484000000b004dc4113f224mr1111332ywd.455.1674065209076; Wed, 18 Jan 2023 10:06:49 -0800 (PST) MIME-Version: 1.0 References: <20230109205336.3665937-1-surenb@google.com> <20230109205336.3665937-27-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Wed, 18 Jan 2023 10:06:38 -0800 Message-ID: Subject: Re: [PATCH 26/41] kernel/fork: assert no VMA readers during its destruction To: Michal Hocko Cc: akpm@linux-foundation.org, michel@lespinasse.org, jglisse@google.com, vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, peterz@infradead.org, ldufour@linux.ibm.com, laurent.dufour@fr.ibm.com, paulmck@kernel.org, luto@kernel.org, songliubraving@fb.com, peterx@redhat.com, david@redhat.com, dhowells@redhat.com, hughd@google.com, bigeasy@linutronix.de, kent.overstreet@linux.dev, punit.agrawal@bytedance.com, lstoakes@gmail.com, peterjung1337@gmail.com, rientjes@google.com, axelrasmussen@google.com, joelaf@google.com, minchan@google.com, jannh@google.com, shakeelb@google.com, tatashin@google.com, edumazet@google.com, gthelen@google.com, gurua@google.com, arjunroy@google.com, soheil@google.com, hughlynch@google.com, leewalsh@google.com, posk@google.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: 6m1gcgxejaqkujh83tf9n55mo54837aj X-Rspam-User: X-Rspamd-Queue-Id: 46456140011 X-Rspamd-Server: rspam06 X-HE-Tag: 1674065210-94242 X-HE-Meta: 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 F4gqb9so EqVAN0ffXLWBo9b8= 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 Wed, Jan 18, 2023 at 1:43 AM 'Michal Hocko' via kernel-team wrote: > > On Tue 17-01-23 17:53:00, Suren Baghdasaryan wrote: > > On Tue, Jan 17, 2023 at 7:42 AM 'Michal Hocko' via kernel-team > > wrote: > > > > > > On Mon 09-01-23 12:53:21, Suren Baghdasaryan wrote: > > > > Assert there are no holders of VMA lock for reading when it is about to be > > > > destroyed. > > > > > > > > Signed-off-by: Suren Baghdasaryan > > > > --- > > > > include/linux/mm.h | 8 ++++++++ > > > > kernel/fork.c | 2 ++ > > > > 2 files changed, 10 insertions(+) > > > > > > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > > > index 594e835bad9c..c464fc8a514c 100644 > > > > --- a/include/linux/mm.h > > > > +++ b/include/linux/mm.h > > > > @@ -680,6 +680,13 @@ static inline void vma_assert_write_locked(struct vm_area_struct *vma) > > > > VM_BUG_ON_VMA(vma->vm_lock_seq != READ_ONCE(vma->vm_mm->mm_lock_seq), vma); > > > > } > > > > > > > > +static inline void vma_assert_no_reader(struct vm_area_struct *vma) > > > > +{ > > > > + VM_BUG_ON_VMA(rwsem_is_locked(&vma->lock) && > > > > + vma->vm_lock_seq != READ_ONCE(vma->vm_mm->mm_lock_seq), > > > > + vma); > > > > > > Do we really need to check for vm_lock_seq? rwsem_is_locked should tell > > > us something is wrong on its own, no? This could be somebody racing with > > > the vma destruction and using the write lock. Unlikely but I do not see > > > why to narrow debugging scope. > > > > I wanted to ensure there are no page fault handlers (read-lockers) > > when we are destroying the VMA and rwsem_is_locked(&vma->lock) alone > > could trigger if someone is concurrently calling vma_write_lock(). But > > I don't think we expect someone to be write-locking the VMA while we > > That would be UAF, no? Yes. That's why what I have is an overkill (which is also racy). > > > are destroying it, so you are right, I'm overcomplicating things here. > > I think I can get rid of vma_assert_no_reader() and add > > VM_BUG_ON_VMA(rwsem_is_locked(&vma->lock)) directly in > > __vm_area_free(). WDYT? > > Yes, that adds some debugging. Not sure it is really necessary buyt it > is VM_BUG_ON so why not. I would like to keep it if possible. If it triggers that would be a clear signal what the issue is. Otherwise it might be hard to debug such a corner case. > -- > Michal Hocko > SUSE Labs > > -- > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. >