linux-kernel - [PATCH 5.4.y 0/3] Backport series: "permit write-sealed memfd read-only shared mappings"

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Message-ID: <20250730005818.2793577-1-isaacmanjarres@google.com>
Date: Tue, 29 Jul 2025 17:58:05 -0700
From: "Isaac J. Manjarres" <isaacmanjarres@...gle.com>
To: lorenzo.stoakes@...cle.com, gregkh@...uxfoundation.org, 
	Muchun Song <muchun.song@...ux.dev>, Oscar Salvador <osalvador@...e.de>, 
	David Hildenbrand <david@...hat.com>, Alexander Viro <viro@...iv.linux.org.uk>, 
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, 
	Andrew Morton <akpm@...ux-foundation.org>, "Liam R. Howlett" <Liam.Howlett@...cle.com>, 
	Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>, 
	Michal Hocko <mhocko@...e.com>, Kees Cook <kees@...nel.org>, Ingo Molnar <mingo@...hat.com>, 
	Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>, 
	Vincent Guittot <vincent.guittot@...aro.org>, Dietmar Eggemann <dietmar.eggemann@....com>, 
	Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, 
	Valentin Schneider <vschneid@...hat.com>, "Matthew Wilcox (Oracle)" <willy@...radead.org>, Jann Horn <jannh@...gle.com>, 
	Pedro Falcato <pfalcato@...e.de>, Hugh Dickins <hughd@...gle.com>, 
	Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: aliceryhl@...gle.com, stable@...r.kernel.org, 
	"Isaac J. Manjarres" <isaacmanjarres@...gle.com>, kernel-team@...roid.com, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: [PATCH 5.4.y 0/3] Backport series: "permit write-sealed memfd
 read-only shared mappings"

Hello,

Until kernel version 6.7, a write-sealed memfd could not be mapped as
shared and read-only. This was clearly a bug, and was not inline with
the description of F_SEAL_WRITE in the man page for fcntl()[1].

Lorenzo's series [2] fixed that issue and was merged in kernel version
6.7, but was not backported to older kernels. So, this issue is still
present on kernels 5.4, 5.10, 5.15, 6.1, and 6.6.

This series backports Lorenzo's series to the 5.4 kernel.

[1] https://man7.org/linux/man-pages/man2/fcntl.2.html
[2] https://lore.kernel.org/all/913628168ce6cce77df7d13a63970bae06a526e0.1697116581.git.lstoakes@gmail.com/T/#m28fbfb0d5727e5693e54a7fb2e0c9ac30e95eca5

Lorenzo Stoakes (3):
  mm: drop the assumption that VM_SHARED always implies writable
  mm: update memfd seal write check to include F_SEAL_WRITE
  mm: perform the mapping_map_writable() check after call_mmap()

 fs/hugetlbfs/inode.c |  2 +-
 include/linux/fs.h   |  4 ++--
 include/linux/mm.h   | 26 +++++++++++++++++++-------
 kernel/fork.c        |  2 +-
 mm/filemap.c         |  2 +-
 mm/madvise.c         |  2 +-
 mm/mmap.c            | 26 ++++++++++++++++----------
 mm/shmem.c           |  2 +-
 8 files changed, 42 insertions(+), 24 deletions(-)

-- 
2.50.1.552.g942d659e1b-goog