The patch below does not apply to the 5.4-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 stable@vger.kernel.org.

thanks,

greg k-h

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

From 1dc1eed46f9fa4cb8a07baa24fb44c96d6dd35c9 Mon Sep 17 00:00:00 2001

From: Miklos Szeredi mszeredi@redhat.com Date: Mon, 27 Sep 2021 11:23:57 +0200 Subject: [PATCH] ovl: fix IOCB_DIRECT if underlying fs doesn't support direct IO

Normally the check at open time suffices, but e.g loop device does set IOCB_DIRECT after doing its own checks (which are not sufficent for overlayfs).

Make sure we don't call the underlying filesystem read/write method with the IOCB_DIRECT if it's not supported.

Reported-by: Huang Jianan huangjianan@oppo.com Fixes: 16914e6fc7e1 ("ovl: add ovl_read_iter()") Cc: stable@vger.kernel.org # v4.19 Tested-by: Huang Jianan huangjianan@oppo.com Signed-off-by: Miklos Szeredi mszeredi@redhat.com

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c index d081faa55e83..c88ac571593d 100644 --- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -296,6 +296,12 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter) if (ret) return ret;

+ ret = -EINVAL; + if (iocb->ki_flags & IOCB_DIRECT && + (!real.file->f_mapping->a_ops || + !real.file->f_mapping->a_ops->direct_IO)) + goto out_fdput; + old_cred = ovl_override_creds(file_inode(file)->i_sb); if (is_sync_kiocb(iocb)) { ret = vfs_iter_read(real.file, iter, &iocb->ki_pos, @@ -320,7 +326,7 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter) out: revert_creds(old_cred); ovl_file_accessed(file); - +out_fdput: fdput(real);

return ret; @@ -349,6 +355,12 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter) if (ret) goto out_unlock;

+ ret = -EINVAL; + if (iocb->ki_flags & IOCB_DIRECT && + (!real.file->f_mapping->a_ops || + !real.file->f_mapping->a_ops->direct_IO)) + goto out_fdput; + if (!ovl_should_sync(OVL_FS(inode->i_sb))) ifl &= ~(IOCB_DSYNC | IOCB_SYNC);

@@ -384,6 +396,7 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter) } out: revert_creds(old_cred); +out_fdput: fdput(real);

out_unlock: