[merged mm-hotfixes-stable] mm-gup-fix-wrongly-calculated-returned-value-in-fault_in_safe_writeable.patch removed from -mm tree

[merged mm-hotfixes-stable] mm-gup-fix-wrongly-calculated-returned-value-in-fault_in_safe_writeable.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm/gup: fix wrongly calculated returned value in fault_in_safe_writeable()
has been removed from the -mm tree.  Its filename was
     mm-gup-fix-wrongly-calculated-returned-value-in-fault_in_safe_writeable.patch

This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Baoquan He <bhe@redhat.com>
Subject: mm/gup: fix wrongly calculated returned value in fault_in_safe_writeable()
Date: Thu, 10 Apr 2025 11:57:14 +0800

Not like fault_in_readable() or fault_in_writeable(), in
fault_in_safe_writeable() local variable 'start' is increased page by page
to loop till the whole address range is handled.  However, it mistakenly
calculates the size of the handled range with 'uaddr - start'.

Fix it here.

Andreas said:

: In gfs2, fault_in_iov_iter_writeable() is used in
: gfs2_file_direct_read() and gfs2_file_read_iter(), so this potentially
: affects buffered as well as direct reads.  This bug could cause those
: gfs2 functions to spin in a loop.

Link: https://lkml.kernel.org/r/20250410035717.473207-1-bhe@redhat.com
Link: https://lkml.kernel.org/r/20250410035717.473207-2-bhe@redhat.com
Signed-off-by: Baoquan He <bhe@redhat.com>
Fixes: fe673d3f5bf1 ("mm: gup: make fault_in_safe_writeable() use fixup_user_fault()")
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Yanjun.Zhu <yanjun.zhu@linux.dev>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/gup.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/gup.c~mm-gup-fix-wrongly-calculated-returned-value-in-fault_in_safe_writeable
+++ a/mm/gup.c
@@ -2207,8 +2207,8 @@ size_t fault_in_safe_writeable(const cha
 	} while (start != end);
 	mmap_read_unlock(mm);
 
-	if (size > (unsigned long)uaddr - start)
-		return size - ((unsigned long)uaddr - start);
+	if (size > start - (unsigned long)uaddr)
+		return size - (start - (unsigned long)uaddr);
 	return 0;
 }
 EXPORT_SYMBOL(fault_in_safe_writeable);
_

Patches currently in -mm which might be from bhe@redhat.com are

mm-gup-remove-unneeded-checking-in-follow_page_pte.patch
mm-gup-remove-gup_fast_pgd_leaf-and-clean-up-the-relevant-codes.patch
mm-gup-clean-up-codes-in-fault_in_xxx-functions.patch
mm-gup-clean-up-codes-in-fault_in_xxx-functions-v5.patch