[alternative-merged] mm-gup_test-fix-race-with-pin_longterm_test-ioctls.patch removed from -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

The quilt patch titled
     Subject: mm/gup_test: fix race with PIN_LONGTERM_TEST ioctls
has been removed from the -mm tree.  Its filename was
     mm-gup_test-fix-race-with-pin_longterm_test-ioctls.patch

This patch was dropped because an alternative patch was or shall be merged

------------------------------------------------------
From: Yunhui Cui <cuiyunhui@bytedance.com>
Subject: mm/gup_test: fix race with PIN_LONGTERM_TEST ioctls
Date: Mon, 8 Jun 2026 10:50:42 +0800

The PIN_LONGTERM_TEST helpers keep their state in global variables that
are protected by pin_longterm_test_mutex when accessed from ioctl(). 
However, gup_test_release() calls pin_longterm_test_stop() without holding
that mutex.

This can race with PIN_LONGTERM_TEST_STOP and let two callers operate on
the same pages array concurrently, corrupting the test state and possibly
freeing it twice:

 CPU 0                              CPU 1
 -----                              -----
 ioctl(PIN_LONGTERM_TEST_STOP)
   mutex_lock(&pin_longterm_test_mutex)
   pin_longterm_test_stop()
     if (pin_longterm_test_pages)
       kvfree(pin_longterm_test_pages)

                                    close()
                                      gup_test_release()
                                        pin_longterm_test_stop()
                                          if (pin_longterm_test_pages)
                                            kvfree(pin_longterm_test_pages)

     pin_longterm_test_pages = NULL
   mutex_unlock(&pin_longterm_test_mutex)

Protect the release path with the same mutex so that stop and release
cannot run pin_longterm_test_stop() concurrently.

John observed "this fix is purely static code analysis hygiene:
correcting a theoretical problem that does not actually provide any
sort of vulnerability fix in the kernel".

Link: https://lore.kernel.org/20260608025043.88087-1-cuiyunhui@bytedance.com
Fixes: c77369b437f9 ("mm/gup_test: start/stop/read functionality for PIN LONGTERM test")
Signed-off-by: Yunhui Cui <cuiyunhui@bytedance.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/gup_test.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/mm/gup_test.c~mm-gup_test-fix-race-with-pin_longterm_test-ioctls
+++ a/mm/gup_test.c
@@ -377,7 +377,9 @@ static long gup_test_ioctl(struct file *
 
 static int gup_test_release(struct inode *inode, struct file *file)
 {
+	mutex_lock(&pin_longterm_test_mutex);
 	pin_longterm_test_stop();
+	mutex_unlock(&pin_longterm_test_mutex);
 
 	return 0;
 }
_

Patches currently in -mm which might be from cuiyunhui@bytedance.com are

riscv-mm-exclude-invalid-thp-pmds-from-page-table-check.patch