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From: Filipe Manana <fdmanana@kernel.org>
To: Eugeniu Rosca <erosca@de.adit-jv.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-btrfs@vger.kernel.org,  stable@vger.kernel.org,
	Maksim Paimushkin <Maksim.Paimushkin@se.bosch.com>,
	 Matthias Thomae <Matthias.Thomae@de.bosch.com>,
	Sebastian Unger <Sebastian.Unger@bosch.com>,
	 Dirk Behme <Dirk.Behme@de.bosch.com>,
	Eugeniu Rosca <Eugeniu.Rosca@bosch.com>,
	 Eugeniu Rosca <roscaeugeniu@gmail.com>
Subject: Re: [PATCH] btrfs: fix infinite directory reads
Date: Thu, 25 Jan 2024 12:04:24 +0000	[thread overview]
Message-ID: <CAL3q7H43=iZxwcXw543TieNz_XadbNgC+_9+tUy6NnsA63TaYQ@mail.gmail.com> (raw)
In-Reply-To: <20240124225522.GA2614102@lxhi-087>

On Wed, Jan 24, 2024 at 10:55 PM Eugeniu Rosca <erosca@de.adit-jv.com> wrote:
>
> Hello Greg,
> Hello Filipe,
>
> On Sun, Aug 13, 2023 at 12:34:08PM +0100, fdmanana@kernel.org wrote:
> > From: Filipe Manana <fdmanana@suse.com>
> >
> > The readdir implementation currently processes always up to the last index
> > it finds. This however can result in an infinite loop if the directory has
> > a large number of entries such that they won't all fit in the given buffer
> > passed to the readdir callback, that is, dir_emit() returns a non-zero
> > value. Because in that case readdir() will be called again and if in the
> > meanwhile new directory entries were added and we still can't put all the
> > remaining entries in the buffer, we keep repeating this over and over.
> >
> > The following C program and test script reproduce the problem:
>
> This crucial fix successfully landed into vanilla v6.5 [1] and stable
> v6.4.12 [2], but unfortunately not into the older stable trees.
>
> Consequently, the fix is missing on the popular Ubuntu versions like
> 20.04 (KNL v5.15.x) and 22.04.3 (KNL v6.2.x). For that reason, people
> still experience infinite loops when building Linux on those systems.
>
> To overcome the issue, people fall back to workarounds [3-4].
>
> The patch seems to apply cleanly to v6.2, but not to v5.15
> (v5.15 backport attempt failed miserably).
>
> Is there a chance for:
>  - Stable maintainers to accept the clean backport to v6.2?
>  - BTRFS experts to suggest a conflict resolution for v5.15?

As mentioned in another thread, here's the backport for 5.15 stable
along with other needed patches:

https://lore.kernel.org/linux-btrfs/cover.1706183427.git.fdmanana@suse.com/

>
> [1] https:// git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9b378f6ad48cfa
> [2] https:// git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5441532ffc9c8c
> [3] https:// android-review.googlesource.com/c/kernel/build/+/2708835
> [4] https:// android-review.googlesource.com/c/kernel/build/+/2715296
>
> Best Regards
> Eugeniu

      reply	other threads:[~2024-01-25 12:05 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-08-13 11:34 [PATCH] btrfs: fix infinite directory reads fdmanana
2023-08-13 18:23 ` Filipe Manana
2023-08-14 14:18 ` David Sterba
2024-01-24 22:55 ` Eugeniu Rosca
2024-01-25 12:04   ` Filipe Manana [this message]

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