linux-kernel - [PATCH v2 0/3] mm/secretmem: one fix and one refactoring

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Date: Tue, 26 Mar 2024 15:32:07 +0100
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org,
	David Hildenbrand <david@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Rapoport <rppt@...nel.org>,
	Miklos Szeredi <mszeredi@...hat.com>,
	Lorenzo Stoakes <lstoakes@...il.com>,
	xingwei lee <xrivendell7@...il.com>,
	yue sun <samsun1006219@...il.com>
Subject: [PATCH v2 0/3] mm/secretmem: one fix and one refactoring

Patch #1 fixes a GUP-fast issue, whereby we might succeed in pinning
secretmem folios. Patch #2 extends the memfd_secret selftest to cover
that case. Patch #3 removes folio_is_secretmem() and instead lets
folio_fast_pin_allowed() cover that case as well.

With this series, the reproducer (+selftests) works as expected. To
test patch #3, the gup_longterm test does exactly what we need, and
keeps on working as expected.

Without the fix:
	TAP version 13
	1..6
	ok 1 mlock limit is respected
	ok 2 file IO is blocked as expected
	not ok 3 vmsplice: unexpected memory access with fresh page
	ok 4 vmsplice is blocked as expected with existing page
	ok 5 process_vm_read is blocked as expected
	ok 6 ptrace is blocked as expected
	# Totals: pass:5 fail:1 xfail:0 xpass:0 skip:0 error:0

With the fix:
	TAP version 13
	1..6
	ok 1 mlock limit is respected
	ok 2 file IO is blocked as expected
	ok 3 vmsplice is blocked as expected with fresh page
	ok 4 vmsplice is blocked as expected with existing page
	ok 5 process_vm_read is blocked as expected
	ok 6 ptrace is blocked as expected
	# Totals: pass:6 fail:0 xfail:0 xpass:0 skip:0 error:0

v1 -> v2:
* "mm/secretmem: fix GUP-fast succeeding on secretmem folios"
 -> Drop the LRU check completely
 -> Rephrase patch description
 -> (Dropped RB from Mike)
* "selftests/memfd_secret: add vmsplice() test"
 -> Add test with fresh+existing page
 -> Change pass/fail message
 -> Rephrase patch description
 -> (Dropped RB from Mike)
* "mm: merge folio_is_secretmem() and folio_fast_pin_allowed() into
   gup_fast_folio_allowed()"
 -> Adjust to dropped LRU check
 -> Rename folio_fast_pin_allowed() to gup_fast_folio_allowed()
 -> Rephrase patch description
 -> Add RB from Mike

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Mike Rapoport (IBM) <rppt@...nel.org>
Cc: Miklos Szeredi <mszeredi@...hat.com>
Cc: Lorenzo Stoakes <lstoakes@...il.com>
Cc: xingwei lee <xrivendell7@...il.com>
Cc: yue sun <samsun1006219@...il.com>

David Hildenbrand (3):
  mm/secretmem: fix GUP-fast succeeding on secretmem folios
  selftests/memfd_secret: add vmsplice() test
  mm: merge folio_is_secretmem() and folio_fast_pin_allowed() into
    gup_fast_folio_allowed()

 include/linux/secretmem.h                 | 21 +---------
 mm/gup.c                                  | 48 ++++++++++++---------
 tools/testing/selftests/mm/memfd_secret.c | 51 ++++++++++++++++++++++-
 3 files changed, 79 insertions(+), 41 deletions(-)

-- 
2.43.2