FAILED: patch "[PATCH] fuse: limit FUSE_NOTIFY_RETRIEVE to uptodate folios" failed to apply to 6.6-stable tree

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 <[email protected]>.

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 4e3d1b2c48ca6c55f1e9ca7f8dccc76f120f276c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026061525-banshee-overlay-7405@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 4e3d1b2c48ca6c55f1e9ca7f8dccc76f120f276c Mon Sep 17 00:00:00 2001
From: Jann Horn <[email protected]>
Date: Tue, 19 May 2026 16:40:34 +0200
Subject: [PATCH] fuse: limit FUSE_NOTIFY_RETRIEVE to uptodate folios

FUSE_NOTIFY_RETRIEVE must be limited to uptodate folios; !uptodate folios can contain uninitialized data.
Since FUSE_NOTIFY_RETRIEVE is intended to only return data that is already in the page cache and not wait for data from the FUSE daemon, treat !uptodate folios as if they weren't present.

This only has security impact on systems that don't enable automatic zero-initialization of all page allocations via CONFIG_INIT_ON_ALLOC_DEFAULT_ON or init_on_alloc=1.

index 5dda7080f4a9..08d364ed7d6c 100644
@@ -1912,6 +1912,10 @@ static int fuse_retrieve(struct fuse_mount *fm, struct inode *inode,
 		folio = filemap_get_folio(mapping, index);
 		if (IS_ERR(folio))
 			break;
+		if (!folio_test_uptodate(folio)) {
+			folio_put(folio);
+			break;
+		}
 
 		folio_offset = offset_in_folio(folio, pos);
 		nr_bytes = min(folio_size(folio) - folio_offset, num);

From: Jann Horn <[email protected]>

[ Upstream commit 4e3d1b2c48ca6c55f1e9ca7f8dccc76f120f276c ]

FUSE_NOTIFY_RETRIEVE must be limited to uptodate folios; !uptodate folios can contain uninitialized data.
Since FUSE_NOTIFY_RETRIEVE is intended to only return data that is already in the page cache and not wait for data from the FUSE daemon, treat !uptodate folios as if they weren't present.

This only has security impact on systems that don't enable automatic zero-initialization of all page allocations via CONFIG_INIT_ON_ALLOC_DEFAULT_ON or init_on_alloc=1.

---
 fs/fuse/dev.c | 4 ++++
 1 file changed, 4 insertions(+)

index 7573dcd8f5d442..b9d6e03f8f7f45 100644
@@ -1718,6 +1718,10 @@ static int fuse_retrieve(struct fuse_mount *fm, struct inode *inode,
 		page = find_get_page(mapping, index);
 		if (!page)
 			break;
+		if (!PageUptodate(page)) {
+			put_page(page);
+			break;
+		}
 
 		this_num = min_t(unsigned, num, PAGE_SIZE - offset);
 		ap->pages[ap->num_pages] = page;

2.53.0