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smtp.kernel.org (Postfix) with ESMTPSA id 88CFAC4CEDD; Tue, 11 Feb 2025 14:01:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1739282470; bh=W4EbBbuyk3MpknoCIOAaHOmpmm2WzX6Vs/PF/x622I4=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=MO1i98QjauLQEkR3Kc2jCjTk4qRtMKjUtLgq+2ba88HwI1W+xtibo+hkFXIqzcOsU ZuoG8c//mA7HBFSDFfxWsZWvivwNXx2UfV8RlcB/sP2i6b5TI7otyrka2jTh+FE8XT JxZbSHESobO3K+X3JaeIiQ17BxxaexGP9eox4IGqjle9Z9oAIUY//CfLJR+Cy3crGz zgFnNV1nVLSo4c/Qt3zUwHK4UzS6dIn2YfeODiEiLtIhwRkplrrSWRhKrUy+aOU3ZA 6zvixRrDRM2B5z8WCWz3qOcCTRJW6WAyCqpULOLh31axI7P958wyOAZNpzXmNNO3sn bUt0vDdyzS7vQ== Message-ID: Subject: Re: [REGRESSION][BISECTED] Crash with Bad page state for FUSE/Flatpak related applications since v6.13 From: Jeff Layton To: Matthew Wilcox , Josef Bacik Cc: Joanne Koong , Vlastimil Babka , 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: Tue, 11 Feb 2025 09:01:08 -0500 In-Reply-To: <8a99f6bf3f0b5cb909f11539fb3b0ef0d65b3a73.camel@kernel.org> References: <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> <8a99f6bf3f0b5cb909f11539fb3b0ef0d65b3a73.camel@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 0OX6MYPtv76hka8lW4mnRmZqqx3UtfHX/hF/zH24Gj7A6sYKYLCU3YrI2Ogiu7/ksKcl7goQjpvtV YrOOI5VGLHge0awt7bhMCTM9KAfPc+xL/ZxAMVWd3NCk5SamL2cE99UWgtvNOIYU8m6EjTLhsj8sn 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 e2xw+0Jy +FEpvPGdN0bsspDMMl/epN0CyGyboMSDaz3aTvVHJkh2n5UmTY7Egh8TKxrGCBHzE6iP4Tv/Nea1haWEoQSFxBAR7KT4Ivu5zZsEfJXTzW+Vrg2hJOzoXVZ/Kz4jdSCcybMrSQm721DFe6HITRDur12xjDmywGzJkfx196BQ7apXF/+o9hqyS0vyb4dfvYIQrPsHDkuVqprNwfO3KFTbVmJOF3E7ElUWnqNT+58C5yfJDekMyL0wmL0ujiAvk1ZDhDnaTgZV4dE+AZ+bCMMMJ/tw7nQnd8EoeweB+3bxIDQ1yv64UeXqqpGgWHphfRCYXidDfyZilhIya7zf6apqqYxasQ7td8qN9Rh4rTxqRH5WNge8= 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: List-Subscribe: List-Unsubscribe: On Mon, 2025-02-10 at 17:38 -0500, Jeff Layton wrote: > On Mon, 2025-02-10 at 20:36 +0000, Matthew Wilcox wrote: > > On Mon, Feb 10, 2025 at 02:12:35PM -0500, Josef Bacik wrote: > > > 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 converte= d > > > us to using the new folio readahead code, which drops the reference o= n > > > 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 o= f > > > 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 f= or > > > 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/2f681f48-00f5-4e09-8431-2= b3dbfaa881e@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_st= ate *cs, struct page **pagep) > > > } > > > =20 > > > folio_unlock(oldfolio); > > > - /* Drop ref for ap->pages[] array */ > > > - folio_put(oldfolio); > > > cs->len =3D 0; > >=20 > > But aren't we now leaking a reference to newfolio? ie shouldn't > > we also: > >=20 > > - folio_get(newfolio); > >=20 > > a few lines earlier? > >=20 >=20 >=20 > I think that ref was leaking without Josef's patch, but your proposed > fix seems correct to me. There is: >=20 > - 1 reference stolen from the pipe_buffer > - 1 reference taken for the pagecache in replace_page_cache_folio() > - the folio_get(newfolio) just after that >=20 > The pagecache ref doesn't count here, and we only need the reference > that was stolen from the pipe_buffer to replace the one in pagep. Actually, no. I'm wrong here. A little after the folio_get(newfolio) call, we do: /* * Release while we have extra ref on stolen page. Otherwise * anon_pipe_buf_release() might think the page can be reused. */ pipe_buf_release(cs->pipe, buf); ...so that accounts for the extra reference. I think the newfolio refcounting is correct as-is. --=20 Jeff Layton