From 02c0cab8e7345b06f1c0838df444e2902e4138d3 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Thu, 21 Jul 2022 16:06:18 +0200 Subject: [PATCH] fuse: ioctl: translate ENOSYS MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Overlayfs may fail to complete updates when a filesystem lacks fileattr/xattr syscall support and responds with an ENOSYS error code, resulting in an unexpected "Function not implemented" error. This bug may occur with FUSE filesystems, such as davfs2. Steps to reproduce: # install davfs2, e.g., apk add davfs2 mkdir /test mkdir /test/lower /test/upper /test/work /test/mnt yes '' | mount -t davfs -o ro http://some-web-dav-server/path \ /test/lower mount -t overlay -o upperdir=/test/upper,lowerdir=/test/lower \ -o workdir=/test/work overlay /test/mnt # when "some-file" exists in the lowerdir, this fails with "Function # not implemented", with dmesg showing "overlayfs: failed to retrieve # lower fileattr (/some-file, err=-38)" touch /test/mnt/some-file The underlying cause of this regresion is actually in FUSE, which fails to translate the ENOSYS error code returned by userspace filesystem (which means that the ioctl operation is not supported) to ENOTTY. Reported-by: Christian Kohlschütter Fixes: 72db82115d2b ("ovl: copy up sync/noatime fileattr flags") Fixes: 59efec7b9039 ("fuse: implement ioctl support") Cc: Signed-off-by: Miklos Szeredi --- fs/fuse/ioctl.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/fs/fuse/ioctl.c b/fs/fuse/ioctl.c index 33cde4bbccdc..61d8afcb10a3 100644 --- a/fs/fuse/ioctl.c +++ b/fs/fuse/ioctl.c @@ -9,6 +9,17 @@ #include #include +static ssize_t fuse_send_ioctl(struct fuse_mount *fm, struct fuse_args *args) +{ + ssize_t ret = fuse_simple_request(fm, args); + + /* Translate ENOSYS, which shouldn't be returned from fs */ + if (ret == -ENOSYS) + ret = -ENOTTY; + + return ret; +} + /* * CUSE servers compiled on 32bit broke on 64bit kernels because the * ABI was defined to be 'struct iovec' which is different on 32bit @@ -259,7 +270,7 @@ long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg, ap.args.out_pages = true; ap.args.out_argvar = true; - transferred = fuse_simple_request(fm, &ap.args); + transferred = fuse_send_ioctl(fm, &ap.args); err = transferred; if (transferred < 0) goto out; @@ -393,7 +404,7 @@ static int fuse_priv_ioctl(struct inode *inode, struct fuse_file *ff, args.out_args[1].size = inarg.out_size; args.out_args[1].value = ptr; - err = fuse_simple_request(fm, &args); + err = fuse_send_ioctl(fm, &args); if (!err) { if (outarg.result < 0) err = outarg.result;