FAILED: patch "[PATCH] mm/madvise: preserve VMA_SOFTDIRTY_BIT when changing anonymous names" failed to apply to 6.6-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 652f15be3c11415725694ccea317c51e35c0b582
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261109201213-failed-6.6-652f15be3c11@kernel.org' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From 652f15be3c11415725694ccea317c51e35c0b582 Mon Sep 17 00:00:00 2001
From: "David Hildenbrand (Arm)" <david@kernel.org>
Date: Fri, 23 Oct 2026 14:47:29 +0100
Subject: [PATCH] mm/madvise: preserve VMA_SOFTDIRTY_BIT when changing
 anonymous names

When changing the anonymous VMA name, madvise_update_vma() calls
vma_modify_name() to possibly merge with adjacent VMAs. We don't call
vma_modify_flags() and consequently don't obtain the new VMA flags.

Later in the function we update the VMA flags to the stale new_vma_flags
we obtained before. This can result in us losing the VMA_SOFTDIRTY_BIT
flag set on a VMA we just merged with.

There is no need to update the VMA flags at all, so just exit early. This
skips calling khugepaged_enter_vma(), but since the flags didn't change
this is fine.

[ljs@kernel.org: minor edit of commit message, rebased]
Link: https://lore.kernel.org/20261023-fix-vma-atomic-v1-3-8ff4fae1fc85@kernel.org
Fixes: 9a10064f5625 ("mm: add a field to store names for private anonymous memory")
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Tested-by: Gregory Price (Meta) <gourry@gourry.net>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Jann Horn <jannh@google.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: SJ Park <sj@kernel.org>
Cc: Kees Cook <kees@kernel.org>
Cc: Colin Cross <ccross@google.com>
Cc: <stable@vger.kernel.org>
---
 mm/madvise.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index b2e00efcaa542..e9fa4f71efeac 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -177,6 +177,9 @@ static int madvise_update_vma(vm_flags_t new_flags,
 
 	/* vm_flags is protected by the mmap_lock held in write mode. */
 	vma_start_write(vma);
+	if (set_new_anon_name)
+		return replace_anon_vma_name(vma, anon_name);
+
 	vma_overwrite_flags(vma, new_vma_flags);
 	/*
 	 * If the vma become good for khugepaged to scan,
@@ -186,9 +189,6 @@ static int madvise_update_vma(vm_flags_t new_flags,
 	if (vma_flags_test(&new_vma_flags, VMA_HUGEPAGE_BIT))
 		khugepaged_enter_vma(vma, vma_flags_to_legacy(new_vma_flags));
 
-	if (set_new_anon_name)
-		return replace_anon_vma_name(vma, anon_name);
-
 	return 0;
 }
 
-- 
2.53.0