FAILED: patch "[PATCH] mm: call ->free_folio() directly in folio_unmap_invalidate()" failed to apply to 6.18-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.18-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-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 615d9bb2ccad42f9e21d837431e401db2e471195
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026042002-idealness-evade-7213@gregkh' --subject-prefix 'PATCH 6.18.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

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

From 615d9bb2ccad42f9e21d837431e401db2e471195 Mon Sep 17 00:00:00 2001
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Date: Mon, 13 Apr 2026 19:43:11 +0100
Subject: [PATCH] mm: call ->free_folio() directly in folio_unmap_invalidate()

We can only call filemap_free_folio() if we have a reference to (or hold a
lock on) the mapping.  Otherwise, we've already removed the folio from the
mapping so it no longer pins the mapping and the mapping can be removed,
causing a use-after-free when accessing mapping->a_ops.

Follow the same pattern as __remove_mapping() and load the free_folio
function pointer before dropping the lock on the mapping.  That lets us
make filemap_free_folio() static as this was the only caller outside
filemap.c.

Link: https://lore.kernel.org/20260413184314.3419945-1-willy@infradead.org
Fixes: fb7d3bc41493 ("mm/filemap: drop streaming/uncached pages when writeback completes")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reported-by: Google Big Sleep <big-sleep-vuln-reports+bigsleep-501448199@google.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/filemap.c b/mm/filemap.c
index 3c1e785542dd..793bf4816ea3 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -228,7 +228,8 @@ void __filemap_remove_folio(struct folio *folio, void *shadow)
 	page_cache_delete(mapping, folio, shadow);
 }
 
-void filemap_free_folio(struct address_space *mapping, struct folio *folio)
+static void filemap_free_folio(const struct address_space *mapping,
+		struct folio *folio)
 {
 	void (*free_folio)(struct folio *);
 
diff --git a/mm/internal.h b/mm/internal.h
index cb0af847d7d9..546114d3ee44 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -540,7 +540,6 @@ unsigned find_lock_entries(struct address_space *mapping, pgoff_t *start,
 		pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices);
 unsigned find_get_entries(struct address_space *mapping, pgoff_t *start,
 		pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices);
-void filemap_free_folio(struct address_space *mapping, struct folio *folio);
 int truncate_inode_folio(struct address_space *mapping, struct folio *folio);
 bool truncate_inode_partial_folio(struct folio *folio, loff_t start,
 		loff_t end);
diff --git a/mm/truncate.c b/mm/truncate.c
index 12467c1bd711..8617a12cb169 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -622,6 +622,7 @@ static int folio_launder(struct address_space *mapping, struct folio *folio)
 int folio_unmap_invalidate(struct address_space *mapping, struct folio *folio,
 			   gfp_t gfp)
 {
+	void (*free_folio)(struct folio *);
 	int ret;
 
 	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
@@ -648,9 +649,12 @@ int folio_unmap_invalidate(struct address_space *mapping, struct folio *folio,
 	xa_unlock_irq(&mapping->i_pages);
 	if (mapping_shrinkable(mapping))
 		inode_lru_list_add(mapping->host);
+	free_folio = mapping->a_ops->free_folio;
 	spin_unlock(&mapping->host->i_lock);
 
-	filemap_free_folio(mapping, folio);
+	if (free_folio)
+		free_folio(folio);
+	folio_put_refs(folio, folio_nr_pages(folio));
 	return 1;
 failed:
 	xa_unlock_irq(&mapping->i_pages);