[PATCH 5.19 0115/1157] fuse: write inode in fuse_release()

Greg Kroah-Hartman
2022-08-15T22:22:59Z

From: Miklos Szeredi <mszeredi@redhat.com>

commit 035ff33cf4db101250fb980a3941bf078f37a544 upstream.

A race between write(2) and close(2) allows pages to be dirtied after
fuse_flush -> write_inode_now(). If these pages are not flushed from
fuse_release(), then there might not be a writable open file later. So any
remaining dirty pages must be written back before the file is released.

This is a partial revert of the blamed commit.

Reported-by: syzbot+6e1efbd8efaaa6860e91@syzkaller.appspotmail.com
Fixes: 36ea23374d1f ("fuse: write inode in fuse_vma_close() instead of fuse_release()")
Cc: <stable@vger.kernel.org> # v5.16
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/fuse/file.c | 9 +++++++++
1 file changed, 9 insertions(+)

--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -338,6 +338,15 @@ static int fuse_open(struct inode *inode

static int fuse_release(struct inode *inode, struct file *file)
{
+ struct fuse_conn *fc = get_fuse_conn(inode);
+
+ /*
+ * Dirty pages might remain despite write_inode_now() call from
+ * fuse_flush() due to writes racing with the close.
+ */
+ if (fc->writeback_cache)
+ write_inode_now(inode, 1);
+
fuse_release_common(file, false);

/* return value is ignored by VFS */