linux-kernel - [PATCH v4 0/2] Cleanup for memfd

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Message-ID: <20250110165904.3437374-1-isaacmanjarres@google.com>
Date: Fri, 10 Jan 2025 08:58:58 -0800
From: "Isaac J. Manjarres" <isaacmanjarres@...gle.com>
To: lorenzo.stoakes@...cle.com, Andrew Morton <akpm@...ux-foundation.org>
Cc: kaleshsingh@...gle.com, jstultz@...gle.com, aliceryhl@...gle.com, 
	surenb@...gle.com, "Isaac J. Manjarres" <isaacmanjarres@...gle.com>, kernel-team@...roid.com, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 0/2] Cleanup for memfd_create()

memfd_create() handles all of its logic in a single function. Some of
the logic in the function is also somewhat contrived (i.e. copying the
memfd name from userpace).

This series aims to cleanup memfd_create() by splitting out the logic
into helper functions, and simplifying the memfd name copying to make
the code easier to follow.

This has no intended functional changes.

Note: to apply this series over mm-unstable, please revert v3 of
the series:

commit 3147192ed457 ("mm/memfd: use strncpy_from_user() to read memfd name")
commit 1212f60db000 ("mm/memfd: refactor and cleanup the logic in memfd_create()")

The base commit from mm-unstable that I used was:

commit 0703fa3785f1 ("mm: remove PageTransTail()")

Thank you Alice and Lorenzo for reviewing v3 of this series and for your
feedback!

Changes from v3 ==> v4:
- Removed an unnecessary comment at the end of memfd_create() that I
  added.
- Added Alice and Lorenzo's "Reviewed-by" tags to both patches in
  the series.
- Rebased on top of the latest commit of the mm-unstable branch as
  mentioned above.

Changes from v2 ==> v3:

- Removed namespacing from the new helper functions names.
- Updated names for helper functions to better describe what they do.
- Changed the argument to the flags sanitization function to be a
  pointer to not discard changes to the flags.
- Restored original ordering of how the fd and file structure were
  allocated.
- Simplified the constant used for allocating the buffer for the memfd
  name to NAME_MAX.
- Updated a comment about the return value of strncpy_from_user().
- Added Alice's "Reviewed-by" tag to the last patch in the series.

Changes from v1 ==> v2:

- Rebased on top of the mm-unstable branch instead of Linus' master
  branch. Base commit on mm-unstable: ca95745c20ad ("mm/memmap: prevent
  double scanning of memmap by kmemleak").

Links:

v1: https://lore.kernel.org/all/20250102230658.1112261-1-isaacmanjarres@google.com/#t
v2: https://lore.kernel.org/all/20250107184804.4074147-1-isaacmanjarres@google.com/
v3: https://lore.kernel.org/all/20250109185908.1006310-1-isaacmanjarres@google.com/

Isaac J. Manjarres (2):
  mm/memfd: Refactor and cleanup the logic in memfd_create()
  mm/memfd: Use strncpy_from_user() to read memfd name

 mm/memfd.c | 95 +++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 61 insertions(+), 34 deletions(-)

-- 
2.47.1.613.gc27f4b7a9f-goog