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[198.145.29.99]) by mx.google.com with ESMTPS id g32si418132pje.38.2019.07.17.14.24.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 17 Jul 2019 14:24:23 -0700 (PDT) Received-SPF: pass (google.com: domain of luto@kernel.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=zh9lxgNm; spf=pass (google.com: domain of luto@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=luto@kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from mail-wr1-f43.google.com (mail-wr1-f43.google.com [209.85.221.43]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3DCBC2187F for ; Wed, 17 Jul 2019 21:24:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563398663; bh=Ap5TwhmtuWKZyNppq7kyJPabjyvLMUE9Mf8WiDtOxmc=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=zh9lxgNm+6nlUVTZWtDHx+bxjyrLvGvPKR7+3Qj2ZiB7xCtjTgsfuX3LelkkwhWiE 939QnXVowCyRxqHZvppFJ44+uvHEp72rB58KK16GnDyDwbc9VtGuMz/1hMzWlf286V 14enB4y9gGoq8PGbGRiqsTA0FC7vu4gonvUFFEPo= Received: by mail-wr1-f43.google.com with SMTP id n9so26413319wru.0 for ; Wed, 17 Jul 2019 14:24:23 -0700 (PDT) X-Received: by 2002:adf:cc85:: with SMTP id p5mr42310193wrj.47.1563398661732; Wed, 17 Jul 2019 14:24:21 -0700 (PDT) MIME-Version: 1.0 References: <20190717071439.14261-1-joro@8bytes.org> <20190717071439.14261-4-joro@8bytes.org> In-Reply-To: <20190717071439.14261-4-joro@8bytes.org> From: Andy Lutomirski Date: Wed, 17 Jul 2019 14:24:09 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 3/3] mm/vmalloc: Sync unmappings in vunmap_page_range() To: Joerg Roedel Cc: Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andrew Morton , LKML , Linux-MM , Joerg Roedel 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 Wed, Jul 17, 2019 at 12:14 AM Joerg Roedel wrote: > > From: Joerg Roedel > > On x86-32 with PTI enabled, parts of the kernel page-tables > are not shared between processes. This can cause mappings in > the vmalloc/ioremap area to persist in some page-tables > after the regions is unmapped and released. > > When the region is re-used the processes with the old > mappings do not fault in the new mappings but still access > the old ones. > > This causes undefined behavior, in reality often data > corruption, kernel oopses and panics and even spontaneous > reboots. > > Fix this problem by activly syncing unmaps in the > vmalloc/ioremap area to all page-tables in the system. > > References: https://bugzilla.suse.com/show_bug.cgi?id=1118689 > Fixes: 5d72b4fba40ef ('x86, mm: support huge I/O mapping capability I/F') > Signed-off-by: Joerg Roedel > --- > mm/vmalloc.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 4fa8d84599b0..322b11a374fd 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -132,6 +132,8 @@ static void vunmap_page_range(unsigned long addr, unsigned long end) > continue; > vunmap_p4d_range(pgd, addr, next); > } while (pgd++, addr = next, addr != end); > + > + vmalloc_sync_all(); > } I'm confused. Shouldn't the code in _vm_unmap_aliases handle this? As it stands, won't your patch hurt performance on x86_64? If x86_32 is a special snowflake here, maybe flush_tlb_kernel_range() should handle this? Even if your patch is correct, a comment would be nice