linux-kernel - [PATCH AUTOSEL 6.10 44/70] fuse: allow O_PATH fd for FUSE_DEV_IOC_BACKING

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Message-ID: <20241004182200.3670903-44-sashal@kernel.org>
Date: Fri,  4 Oct 2024 14:20:42 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Miklos Szeredi <mszeredi@...hat.com>,
	Amir Goldstein <amir73il@...il.com>,
	Sasha Levin <sashal@...nel.org>,
	miklos@...redi.hu,
	linux-fsdevel@...r.kernel.org
Subject: [PATCH AUTOSEL 6.10 44/70] fuse: allow O_PATH fd for FUSE_DEV_IOC_BACKING_OPEN

From: Miklos Szeredi <mszeredi@...hat.com>

[ Upstream commit efad7153bf93db8565128f7567aab1d23e221098 ]

Only f_path is used from backing files registered with
FUSE_DEV_IOC_BACKING_OPEN, so it makes sense to allow O_PATH descriptors.

O_PATH files have an empty f_op, so don't check read_iter/write_iter.

Reviewed-by: Amir Goldstein <amir73il@...il.com>
Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/fuse/passthrough.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/fs/fuse/passthrough.c b/fs/fuse/passthrough.c
index 9666d13884ce5..62aee8289d110 100644
--- a/fs/fuse/passthrough.c
+++ b/fs/fuse/passthrough.c
@@ -228,16 +228,13 @@ int fuse_backing_open(struct fuse_conn *fc, struct fuse_backing_map *map)
 	if (map->flags || map->padding)
 		goto out;
 
-	file = fget(map->fd);
+	file = fget_raw(map->fd);
 	res = -EBADF;
 	if (!file)
 		goto out;
 
-	res = -EOPNOTSUPP;
-	if (!file->f_op->read_iter || !file->f_op->write_iter)
-		goto out_fput;
-
 	backing_sb = file_inode(file)->i_sb;
+	pr_info("%s: %x:%pD %i\n", __func__, backing_sb->s_dev, file, backing_sb->s_stack_depth);
 	res = -ELOOP;
 	if (backing_sb->s_stack_depth >= fc->max_stack_depth)
 		goto out_fput;
-- 
2.43.0