[PATCH 6.1.y 2/2] bs/ntfs3: fix NULL folio dereference in ntfs_lock_new_page()

[Elliot Berman <elliotjb@elliotjb.com>]

In 6.1, __filemap_get_folio() returns NULL on failure.  The backport of
commit 95b917a14b15 ("ntfs: Do not overwrite uptodate pages") keeps the
original IS_ERR() check, which is always false here, so a failed folio
allocation while reading a compressed file dereferences NULL in
folio_test_uptodate(). Check for NULL and return ERR_PTR(-ENOMEM).

Fixes: 95b917a14b15 ("ntfs: Do not overwrite uptodate pages")
Signed-off-by: Elliot Berman <elliotjb@elliotjb.com>
---
 fs/ntfs3/frecord.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ntfs3/frecord.c b/fs/ntfs3/frecord.c
index a44b7338621e..fa443144f6d1 100644
--- a/fs/ntfs3/frecord.c
+++ b/fs/ntfs3/frecord.c
@@ -2172,8 +2172,8 @@ static struct page *ntfs_lock_new_page(struct address_space *mapping,
 			FGP_LOCK | FGP_ACCESSED | FGP_CREAT, gfp);
 	struct page *page;
 
-	if (IS_ERR(folio))
-		return ERR_CAST(folio);
+	if (!folio)
+		return ERR_PTR(-ENOMEM);
 
 	if (!folio_test_uptodate(folio))
 		return folio_file_page(folio, index);

-- 
2.54.0