From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4718626B0A9 for ; Thu, 3 Sep 2026 07:57:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.72 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788422271; cv=none; b=eeskfdlRzO1RD4ADHsy5Fhdy4Cv2VEEIQK5KIM6zYdID8GJS186LSnXZePUF87nL6LIDVW3NfRUpRt/BEejRr4gfuhB7TkHlbd+I8W+9hySVe12bEcBydrzt061IuTWUmp/g16AuDGlzk9G3Ds0LIH/6ZJCDSbXzAYZxG5M3VrE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788422271; c=relaxed/simple; bh=L/r7m7kDv0omebnD1y3qb2AQBcATiYqlgqTB+1Do+6A=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=jDZ+wRAugoT8TkrqGmmm0q4Qf9xJmEENNpxNfSWL0LiDgN5NZJsOUuK0F8J9J70iHmVmb9ohHQCGaxa605dEDx3vyPsGo5xqy5c34jKHjt/LJVARH69NRrJ/iYtxF339iP5EUFEqqtlnTJIXsj+/a3vKUZA3Qd75vwRZwo0qFEw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--aliceryhl.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=Z3SQ4yOk; arc=none smtp.client-ip=209.85.128.72 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--aliceryhl.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Z3SQ4yOk" Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-49ccf17d3b0so12672145e9.3 for ; Thu, 03 Sep 2026 00:57:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1788422268; x=1789027068; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=vR1Q5C1h3ZhnEFmXm0MTEkgQW02wtj80tGssKs7CjOM=; b=Z3SQ4yOkkmXjtWozFUVfzGIYasJxwYZvD5s2E7jaJaJuxGMCZ6GyyyChyz8PKJ9oCJ rWRYPCJdnVitIyT4MuBFZCw5hwI36LBthrxrs27ateKZLinSQQ4RN467ZWT6QJw0RAYT Je1y015IlExYTJC7v2KK6xPt0SS6gj7KKpTfQ8mx8CWZ9PtQ3pxqdjF/rNU0fHxxVDIx wpuk+PusRDJGLBzdPo2TvWiwkdlpBx+PkNN0RqaFpdqz0Ayraen1VYCqBBBBP0lBWk8x 6lJjoXiJzrqtMi6AkeVIfabPgAVicmLXi1vDcGcVMNPSSyehcwv89L+HsjZf/PVC3ADZ LfJA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1788422268; x=1789027068; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=vR1Q5C1h3ZhnEFmXm0MTEkgQW02wtj80tGssKs7CjOM=; b=ev94lis6QR/hpSaihHnPyEjSyFgJh1irLWOHLYidMUJjuWWDJs6Iczx9hQ6wzLIJCz GFgk7pNg61VRYCtGdZ0bj28QDsKPJDM/H79hQZT7sicLxPIwjb1q3fxVdqlKP8BIAGM6 gPD5lZBoSRAwQQcqdRPmLzwrCPS17nQfuGVMGZ5y7Pg1p1r8z9ml+aadUIeglEyhjkeo O1KSvxiX068QRl6RqWEsNQiuxp+ZeIRie8CmzsJj64XSYT6QjHdJd4M2FxsJhDjGohez 0q5xBaVWCcBA1njAX8JsLyo537YdYwd4ddDqov2gO99l2BcSBO2emThWMGrwgSdv6uny uGpQ== X-Forwarded-Encrypted: i=1; AKwUvBzCyYC5MB8ESVpADQwsUAXQ8artv2GdvvVPB2zxSAP1CkUorRI0wnX1Hh+FU8c1VtqnUhP7j3nZYKtinNc=@vger.kernel.org X-Gm-Message-State: AFuF++n3Z45oVHBRvmZtzeGskfMpV4FaFd/UoOqM15coxghim9dEgSXC 2ZrzAO5B0f/0xVEbGO9olTEscMTmWbn33p48N2PBuiS/XnMBKHRm0cdQ20H2TKZ+lfLsocIh8o5 edQhHzwH8W9KMbUTxTA== X-Received: from wmnl19.prod.google.com ([2002:a05:600c:16d3:b0:49c:d53d:56b2]) (user=aliceryhl job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:6209:b0:495:4d5c:903e with SMTP id 5b1f17b1804b1-49ce582039fmr193039575e9.7.1788422268362; Thu, 03 Sep 2026 00:57:48 -0700 (PDT) Date: Thu, 3 Sep 2026 07:57:47 +0000 In-Reply-To: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260901205250.1638304-1-cmllamas@google.com> <20260901205250.1638304-6-cmllamas@google.com> Message-ID: Subject: Re: [PATCH v4 5/7] binder: check vma->vm_start in binder_vma_close() From: Alice Ryhl To: Carlos Llamas Cc: Greg Kroah-Hartman , "Arve =?utf-8?B?SGrDuG5uZXbDpWc=?=" , Todd Kjos , Christian Brauner , kernel-team@android.com, linux-kernel@vger.kernel.org, Suren Baghdasaryan , stable@vger.kernel.org, Sashiko Content-Type: text/plain; charset="utf-8" On Wed, Sep 02, 2026 at 04:25:39PM +0000, Carlos Llamas wrote: > On Wed, Sep 02, 2026 at 12:50:20PM +0000, Alice Ryhl wrote: > > On Tue, Sep 01, 2026 at 08:52:45PM +0000, Carlos Llamas wrote: > > > Certain operations like a failed mremap() might trigger vm_ops->close() > > > on temporary mappings. To avoid tearing-down the main binder mapping on > > > these, let's verify that the VMA matches the expected starting address. > > > > > > Cc: stable@vger.kernel.org > > > Fixes: 457b9a6f09f0 ("Staging: android: add binder driver") > > > Reported-by: Sashiko > > > Closes: https://sashiko.dev/#/patchset/20260831224145.169403-1-cmllamas@google.com?part=1 > > > Signed-off-by: Carlos Llamas > > > --- > > > drivers/android/binder.c | 3 +++ > > > 1 file changed, 3 insertions(+) > > > > > > diff --git a/drivers/android/binder.c b/drivers/android/binder.c > > > index 185128577829..3d359490436e 100644 > > > --- a/drivers/android/binder.c > > > +++ b/drivers/android/binder.c > > > @@ -6018,6 +6018,9 @@ static void binder_vma_close(struct vm_area_struct *vma) > > > { > > > struct binder_proc *proc = vma->vm_private_data; > > > > > > + if (vma->vm_start != proc->alloc.vm_start) > > > + return; > > > > So .. this does work in the case of mremap, but how about instead doing > > this? > > > > static int binder_mremap(struct vm_area_struct *vma) > > { > > vma->vm_private_data = NULL; > > return -EINVAL; > > } > > > > and then check for NULL in binder_vma_close() instead? I think that > > logic would be a bit easier to understand. > > Yeah, I agree that is easier to read. However, not all exit paths that > close a copied vma actually call op->mremap(). We would miss those and > accidentally brick binder. What about setting it to NULL in op->open(), then? Alice > Maybe I should add a comment to the check, so that is easier to read? > > /* > * Ignore temporary vma copies from aborted operations (e.g. > * mremap). Only tear-down the original VMA with the expected > * starting address. > */ > if (vma->vm_start != proc->alloc.vm_start) > return; > > Would that work?