linux-kernel - [PATCH 0/5] fs: Do not allow get_file() to resurrect 0 f

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Message-Id: <20240502222252.work.690-kees@kernel.org>
Date: Thu,  2 May 2024 15:33:35 -0700
From: Kees Cook <keescook@...omium.org>
To: Christian Brauner <brauner@...nel.org>,
	Will Deacon <will@...nel.org>
Cc: Kees Cook <keescook@...omium.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Jan Kara <jack@...e.cz>,
	Zack Rusin <zack.rusin@...adcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Daniel Vetter <daniel@...ll.ch>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Tvrtko Ursulin <tursulin@...ulin.net>,
	Andi Shyti <andi.shyti@...ux.intel.com>,
	Lucas De Marchi <lucas.demarchi@...el.com>,
	Matt Atwood <matthew.s.atwood@...el.com>,
	Matthew Auld <matthew.auld@...el.com>,
	Nirmoy Das <nirmoy.das@...el.com>,
	Jonathan Cavitt <jonathan.cavitt@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Mark Rutland <mark.rutland@....com>,
	Kent Overstreet <kent.overstreet@...ux.dev>,
	Masahiro Yamada <masahiroy@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nicolas Schier <nicolas@...sle.eu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	intel-gfx@...ts.freedesktop.org,
	linux-kbuild@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH 0/5] fs: Do not allow get_file() to resurrect 0 f_count

Hi,

Failure with f_count reference counting are better contained by
an actual reference counting type, like refcount_t. The first step
is for get_file() to use inc_not_zero to avoid resurrection. I also
found a couple open-coded modifications of f_count that should be using
get_file(). Since long ago, f_count was switched to atomic_long_t, so to
get proper reference count checking, I've added a refcount_long_t API,
and then converted f_count to refcount_long_t.

Now if there are underflows (or somehow an overflow), we'll see them
reported.

-Kees

Kees Cook (5):
  fs: Do not allow get_file() to resurrect 0 f_count
  drm/vmwgfx: Do not directly manipulate file->f_count
  drm/i915: Do not directly manipulate file->f_count
  refcount: Introduce refcount_long_t and APIs
  fs: Convert struct file::f_count to refcount_long_t

 MAINTAINERS                           |   2 +-
 Makefile                              |  11 +-
 drivers/gpu/drm/i915/gt/shmem_utils.c |   5 +-
 drivers/gpu/drm/vmwgfx/ttm_object.c   |   2 +-
 fs/file.c                             |   4 +-
 fs/file_table.c                       |   6 +-
 include/linux/fs.h                    |   7 +-
 include/linux/refcount-impl.h         | 344 ++++++++++++++++++++++++++
 include/linux/refcount.h              | 341 +------------------------
 include/linux/refcount_types.h        |  12 +
 lib/refcount.c                        |  17 +-
 11 files changed, 398 insertions(+), 353 deletions(-)
 create mode 100644 include/linux/refcount-impl.h

-- 
2.34.1