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by smtp.kernel.org (Postfix) with ESMTPSA id 77291C4CED1; Mon, 10 Feb 2025 22:38:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1739227123; bh=3UfYaDjfrf1YhQqNf3Bmv7nNKAkbwAh+C1Ay81fdYXQ=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=Ay2ojMal78Os/uTZK5tTgZ7XqjpPplrxyL9hZ5H0DMvCAt8Wy1im2zUku8kjAJgdR VmIO/Vt9o08LMG1/wDx7pM9wj8h6fWHw3m/oC1ed/ncUNbxUV02/8TK+sOoOad2i2h KagA1t2mtb+xtk3nRWkndmC06eXBEtLdAq8SrI4FzZV3TvrgWU9Yo1pB8zJkPXewJ1 ayZksZtyvKNUCipGpUZDIA6wAiHujYh1fUsS4KxfiDcR12XrT34tBiYINDQqIwDNlH PtkTfLMrQDewZHTWrmukJKAxiRtYo75bO/3QuxOnZWNFs+IA5NQcFvKUKLSVW/sJcv HZrXZXFx2zXsQ== Message-ID: <8a99f6bf3f0b5cb909f11539fb3b0ef0d65b3a73.camel@kernel.org> 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: Mon, 10 Feb 2025 17:38:39 -0500 In-Reply-To: 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> 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 VluJH0/RcxEeFbnSaswVChNSGa7mXJrTR22lRL6ZPjdMgS2Km90haWPRc8Wolcz07Y2se0xpGVLEQ 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 rjOkVaTU ARHFMItuOtIAfKpayg2Vid5dK+Q4a0Fd5O4F9J2yC/qyvxk2FYthqOK02gl8VegcLieIGXtXvcWpb+RhH4B9ME8bbkkXshkWQW8JdewmTH6jC8gZznF1vZl6r+hEQcFr7A17JUfFuaz/EfZ/6VaCa6p0PIbSZgVYRS08NkvRN84Katf/kR7GIn+6upHPodQ9kNgTEeCBi4ZJX58j8wobfoBfAU7fPZYDj2hpDo3IqIlnf/D85gkHteFcfe8lOhpUCOXzCwi3ZhSE1juJcwtf27Lu2GU2Lu2lKOrq2oB6FRaKMCZ+isWH9xyqTQrPAu4khe7A3f543+gxKSGeRnRJLVOYq3eLbOfiSvooiUu94aN9BQgs= 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 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 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/2f681f48-00f5-4e09-8431-2b3= dbfaa881e@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_stat= e *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 I think that ref was leaking without Josef's patch, but your proposed fix seems correct to me. There is: - 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 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. --=20 Jeff Layton