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[209.85.220.65]) by mx.google.com with SMTPS id i16sor264677ljj.1.2019.05.08.21.43.05 for (Google Transport Security); Wed, 08 May 2019 21:43:05 -0700 (PDT) Received-SPF: pass (google.com: domain of jrdr.linux@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b="Lt/DTI5w"; spf=pass (google.com: domain of jrdr.linux@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=jrdr.linux@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=e3NuoyA6DsdN8vS1rlRQd+bW+avLSVguOFGnQl9Uq1o=; b=Lt/DTI5wNAIhQ/6m6siviyT/JhbAp3rvLyUD63xEOH2IAg2pMCbMTS5GVTmn+YjFEr pnlVWawZ4nlMIvBOt171hzqJoikbtkxHGB0/mAiy4+T0Rw2CoC2QP83rkkwOknkyTrVW IRuOvLBwGlgkRwVCBqoWuPwWjarfOB15lA5TfomCotP/1mkZgzE2vDNTJwjtVgAPyFrS MJpWxa//z66mbSVrM03P8D5yOr826PzQmL+znaT8rF9P0GSt8GxB25i3hV1aFx4c6bFG 01Sw6nLVbznCBMk4a/bLRUHhV8ZEFJoUM3gjiFpUeSDeboJ9cpOKY0J2miFZ1Gf+wdk2 AoeQ== X-Google-Smtp-Source: APXvYqyahlAiHd3my+REndsaCdCPgpOP53l6bfy+BbUj2xIO/9159X2NF1ynIXXakgT60wBBaFKFYZTmcckc0FIv784= X-Received: by 2002:a2e:7e0a:: with SMTP id z10mr855035ljc.9.1557376985164; Wed, 08 May 2019 21:43:05 -0700 (PDT) MIME-Version: 1.0 References: <20190506232942.12623-1-rcampbell@nvidia.com> <20190506232942.12623-5-rcampbell@nvidia.com> In-Reply-To: From: Souptick Joarder Date: Thu, 9 May 2019 10:12:52 +0530 Message-ID: Subject: Re: [PATCH 4/5] mm/hmm: hmm_vma_fault() doesn't always call hmm_range_unregister() To: Ralph Campbell Cc: Linux-MM , linux-kernel@vger.kernel.org, John Hubbard , Ira Weiny , Dan Williams , Arnd Bergmann , Balbir Singh , Dan Carpenter , Matthew Wilcox , Andrew Morton Content-Type: text/plain; charset="UTF-8" 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 Tue, May 7, 2019 at 11:42 PM Ralph Campbell wrote: > > > On 5/7/19 6:15 AM, Souptick Joarder wrote: > > On Tue, May 7, 2019 at 5:00 AM wrote: > >> > >> From: Ralph Campbell > >> > >> The helper function hmm_vma_fault() calls hmm_range_register() but is > >> missing a call to hmm_range_unregister() in one of the error paths. > >> This leads to a reference count leak and ultimately a memory leak on > >> struct hmm. > >> > >> Always call hmm_range_unregister() if hmm_range_register() succeeded. > > > > How about * Call hmm_range_unregister() in error path if > > hmm_range_register() succeeded* ? > > Sure, sounds good. > I'll include that in v2. Thanks. > > >> > >> Signed-off-by: Ralph Campbell > >> Cc: John Hubbard > >> Cc: Ira Weiny > >> Cc: Dan Williams > >> Cc: Arnd Bergmann > >> Cc: Balbir Singh > >> Cc: Dan Carpenter > >> Cc: Matthew Wilcox > >> Cc: Souptick Joarder > >> Cc: Andrew Morton > >> --- > >> include/linux/hmm.h | 3 ++- > >> 1 file changed, 2 insertions(+), 1 deletion(-) > >> > >> diff --git a/include/linux/hmm.h b/include/linux/hmm.h > >> index 35a429621e1e..fa0671d67269 100644 > >> --- a/include/linux/hmm.h > >> +++ b/include/linux/hmm.h > >> @@ -559,6 +559,7 @@ static inline int hmm_vma_fault(struct hmm_range *range, bool block) > >> return (int)ret; > >> > >> if (!hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT)) { > >> + hmm_range_unregister(range); > >> /* > >> * The mmap_sem was taken by driver we release it here and > >> * returns -EAGAIN which correspond to mmap_sem have been > >> @@ -570,13 +571,13 @@ static inline int hmm_vma_fault(struct hmm_range *range, bool block) > >> > >> ret = hmm_range_fault(range, block); > >> if (ret <= 0) { > >> + hmm_range_unregister(range); > > > > what is the reason to moved it up ? > > I moved it up because the normal calling pattern is: > down_read(&mm->mmap_sem) > hmm_vma_fault() > hmm_range_register() > hmm_range_fault() > hmm_range_unregister() > up_read(&mm->mmap_sem) > > I don't think it is a bug to unlock mmap_sem and then unregister, > it is just more consistent nesting. Ok. I think, adding it in change log will be helpful :) > > >> if (ret == -EBUSY || !ret) { > >> /* Same as above, drop mmap_sem to match old API. */ > >> up_read(&range->vma->vm_mm->mmap_sem); > >> ret = -EBUSY; > >> } else if (ret == -EAGAIN) > >> ret = -EBUSY; > >> - hmm_range_unregister(range); > >> return ret; > >> } > >> return 0; > >> -- > >> 2.20.1 > >>