From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 07E8E24C68B; Mon, 10 Feb 2025 19:42:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739216552; cv=none; b=KDeFEHTRdJF7kw6vZf5uzcJ/hk3gL71VQD5t7QU3ssB93WuShKMpXr887hNgX91G5lenk0EMYEkLA/uXJjyasfplKMuVNACDcJdW6OtCpGeBt7F4YL7Y64e/tMvcunE/2Q/Cw0N0Ln86QQhMqniPz3rm/Es5S2i8QG1VjEoonIc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739216552; c=relaxed/simple; bh=iHTa3v6bu6Wa114W+rf3gxvNsMEALCyX/v82IapYydQ=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=LWUS6Jfo1cGyzjuUTvXWnn2NVwJVZZJ7dMlZsTc/iJaAiR/rPU3ToWNrk+k+WVfu5cZgpuxcLUo2YhIo1wO8P/Cv1AsWYmdOJnh8g3UjkIQZq2rE3tqssmyoandH17eSndw9tat92ePZ5TIs9agmBHGA2qxQWqwECOwXsB7nD8o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Sq/ftJ6l; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Sq/ftJ6l" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 69BACC4CED1; Mon, 10 Feb 2025 19:42:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1739216551; bh=iHTa3v6bu6Wa114W+rf3gxvNsMEALCyX/v82IapYydQ=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=Sq/ftJ6lsZJdEtXnImb/P4VZviY7nXmGEQy9kAyjsJE7WMyOZ0jOKdcaqolnlpLv4 tFtFY5Foo6EPNQQNP0f2CJ2BE1qW9pW+NZataljEBFcKMo0h+4P6p0q+d71nmDnYcX KOPaimrVvFcGCR5OWIe6E7AXcjTOqb3tuhoW6/6N+dIPNgewKoVpcDCTuJ2HlOyAfb 1DBlqNILdRTU1BsIiS15rjuD+a+8IIqlrmW+aworIjjQJjztSZs9Zpr1einHbuxsjf 8wvtxEFGq6wgo2JUwColvgjhkGVIvdPi/VpimCg7QVf0+a7ALBqQQLQhFZ5lSZM0u0 7xsV7ST959Ltg== Message-ID: <87c9118a4456c008d321215cb4632055ce3e2204.camel@kernel.org> Subject: Re: [REGRESSION][BISECTED] Crash with Bad page state for FUSE/Flatpak related applications since v6.13 From: Jeff Layton To: Josef Bacik , Joanne Koong Cc: Vlastimil Babka , Matthew Wilcox , Miklos Szeredi , Christian Heusel , Miklos Szeredi , regressions@lists.linux.dev, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm , Mantas =?UTF-8?Q?Mikul=C4=97nas?= Date: Mon, 10 Feb 2025 14:42:27 -0500 In-Reply-To: <20250210191235.GA2256827@perftesting> References: <2f681f48-00f5-4e09-8431-2b3dbfaa881e@heusel.eu> <9cd88643-daa8-4379-be0a-bd31de277658@suse.cz> <20250207172917.GA2072771@perftesting> <8f7333f2-1ba9-4df4-bc54-44fd768b3d5b@suse.cz> <81298bd1-e630-4940-ae5b-7882576b6bf4@suse.cz> <20250210191235.GA2256827@perftesting> Autocrypt: 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text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-1.fc41) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2025-02-10 at 14:12 -0500, Josef Bacik wrote: > On Mon, Feb 10, 2025 at 10:13:51AM -0800, Joanne Koong wrote: > > On Mon, Feb 10, 2025 at 12:27=E2=80=AFAM Vlastimil Babka wrote: > > >=20 > > > On 2/8/25 16:46, Joanne Koong wrote: > > > > On Sat, Feb 8, 2025 at 2:11=E2=80=AFAM Matthew Wilcox wrote: > > > > >=20 > > > > > On Fri, Feb 07, 2025 at 04:22:56PM -0800, Joanne Koong wrote: > > > > > > > Thanks, Josef. I guess we can at least try to confirm we're o= n the right track. > > > > > > > Can anyone affected see if this (only compile tested) patch f= ixes the issue? > > > > > > > Created on top of 6.13.1. > > > > > >=20 > > > > > > This fixes the crash for me on 6.14.0-rc1. I ran the repro usin= g > > > > > > Mantas's instructions for Obfuscate. I was able to trigger the = crash > > > > > > on a clean build and then with this patch, I'm not seeing the c= rash > > > > > > anymore. > > > > >=20 > > > > > Since this patch fixes the bug, we're looking for one call to fol= io_put() > > > > > too many. Is it possibly in fuse_try_move_page()? In particular= , this > > > > > one: > > > > >=20 > > > > > /* Drop ref for ap->pages[] array */ > > > > > folio_put(oldfolio); > > > > >=20 > > > > > I don't know fuse very well. Maybe this isn't it. > > > >=20 > > > > Yeah, this looks it to me. We don't grab a folio reference for the > > > > ap->pages[] array for readahead and it tracks with Mantas's > > > > fuse_dev_splice_write() dmesg. this patch fixed the crash for me wh= en > > > > I tested it yesterday: > > > >=20 > > > > diff --git a/fs/fuse/file.c b/fs/fuse/file.c > > > > index 7d92a5479998..172cab8e2caf 100644 > > > > --- a/fs/fuse/file.c > > > > +++ b/fs/fuse/file.c > > > > @@ -955,8 +955,10 @@ static void fuse_readpages_end(struct fuse_mou= nt > > > > *fm, struct fuse_args *args, > > > > fuse_invalidate_atime(inode); > > > > } > > > >=20 > > > > - for (i =3D 0; i < ap->num_folios; i++) > > > > + for (i =3D 0; i < ap->num_folios; i++) { > > > > folio_end_read(ap->folios[i], !err); > > > > + folio_put(ap->folios[i]); > > > > + } > > > > if (ia->ff) > > > > fuse_file_put(ia->ff, false); > > > >=20 > > > > @@ -1049,6 +1051,7 @@ static void fuse_readahead(struct readahead_c= ontrol *rac) > > > >=20 > > > > while (ap->num_folios < cur_pages) { > > > > folio =3D readahead_folio(rac); > > > > + folio_get(folio); > > >=20 > > > This is almost the same as my patch, but balances the folio_put() in > > > readahead_folio() with another folio_get(), while mine uses > > > __readahead_folio() that does not do folio_put() in the first place. > > >=20 > > > But I think neither patch proves the extraneous folio_put() comes fro= m > > > fuse_try_move_page(). > > >=20 > > > > ap->folios[ap->num_folios] =3D folio; > > > > ap->descs[ap->num_folios].length =3D folio_= size(folio); > > > > ap->num_folios++; > > > >=20 > > > >=20 > > > > I reran it just now with a printk by that ref drop in > > > > fuse_try_move_page() and I'm indeed seeing that path get hit. > > >=20 > > > It might get hit, but is it hit in the readahead paths? One way to te= st > > > would be to instead of yours above or mine change, to stop doing the > > > foio_put() in fuse_try_move_page(). But maybe it's called also from o= ther > > > contexts that do expect it, and will leak memory otherwise. > >=20 > > When I tested it a few days ago, I printk-ed the address of the folio > > and it matched in fuse_readahead() and try_move_page(). I think that > > proves that the extra folio_put() came from fuse_try_move_page() > > through the readahead path. >=20 > This patch should fix the problem, let me know if it's stil happening >=20 > From 964c798ee9e8f2e8e2c37cfd060c76a772cc45b7 Mon Sep 17 00:00:00 2001 > Message-ID: <964c798ee9e8f2e8e2c37cfd060c76a772cc45b7.1739214698.git.jose= f@toxicpanda.com> > From: Josef Bacik > Date: Mon, 10 Feb 2025 14:06:40 -0500 > Subject: [PATCH] fuse: drop extra put of folio when using pipe splice >=20 > In 3eab9d7bc2f4 ("fuse: convert readahead to use folios"), I converted > us to using the new folio readahead code, which drops the reference on > the folio once it is locked, using an inferred reference on the folio. > Previously we held a reference on the folio for the entire duration of > the readpages call. >=20 > This is fine, however I failed to catch the case for splice pipe > responses where we will remove the old folio and splice in the new > folio. Here we assumed that there is a reference held on the folio for > ap->folios, which is no longer the case. >=20 > To fix this, simply drop the extra put to keep us consistent with the > non-splice variation. This will fix the UAF bug that was reported. >=20 > Link: https://lore.kernel.org/linux-fsdevel/2f681f48-00f5-4e09-8431-2b3db= faa881e@heusel.eu/ > Fixes: 3eab9d7bc2f4 ("fuse: convert readahead to use folios") > Signed-off-by: Josef Bacik > --- > fs/fuse/dev.c | 2 -- > 1 file changed, 2 deletions(-) >=20 > diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c > index 5b5f789b37eb..5bd6e2e184c0 100644 > --- a/fs/fuse/dev.c > +++ b/fs/fuse/dev.c > @@ -918,8 +918,6 @@ static int fuse_try_move_page(struct fuse_copy_state = *cs, struct page **pagep) > } > =20 > folio_unlock(oldfolio); > - /* Drop ref for ap->pages[] array */ > - folio_put(oldfolio); > cs->len =3D 0; > =20 > err =3D 0; Reviewed-by: Jeff Layton