ovl: properly handle large files in ovl_security_fileattr

JIRA: https://issues.redhat.com/browse/RHEL-83562

commit 3b6b99e
Author: Oleksandr Tymoshenko <ovt@google.com>
Date:   Wed Oct 30 00:28:55 2024 +0000

    ovl: properly handle large files in ovl_security_fileattr

    dentry_open in ovl_security_fileattr fails for any file
    larger than 2GB if open method of the underlying filesystem
    calls generic_file_open (e.g. fusefs).

    The issue can be reproduce using the following script:
    (passthrough_ll is an example app from libfuse).

      $ D=/opt/test/mnt
      $ mkdir -p ${D}/{source,base,top/uppr,top/work,ovlfs}
      $ dd if=/dev/zero of=${D}/source/zero.bin bs=1G count=2
      $ passthrough_ll -o source=${D}/source ${D}/base
      $ mount -t overlay overlay \
          -olowerdir=${D}/base,upperdir=${D}/top/uppr,workdir=${D}/top/work \
          ${D}/ovlfs
      $ chmod 0777 ${D}/mnt/ovlfs/zero.bin

    Running this script results in "Value too large for defined data type"
    error message from chmod.

    Signed-off-by: Oleksandr Tymoshenko <ovt@google.com>
    Fixes: 72db821 ("ovl: copy up sync/noatime fileattr flags")
    Cc: stable@vger.kernel.org # v5.15+
    Signed-off-by: Amir Goldstein <amir73il@gmail.com>

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Author: Miklos Szeredi

fs/overlayfs/inode.c

@@ -616,8 +616,13 @@ static int ovl_security_fileattr(const struct path *realpath, struct fileattr *f
 	struct file *file;
 	unsigned int cmd;
 	int err;
+	unsigned int flags;
+
+	flags = O_RDONLY;
+	if (force_o_largefile())
+		flags |= O_LARGEFILE;
 
-	file = dentry_open(realpath, O_RDONLY, current_cred());
+	file = dentry_open(realpath, flags, current_cred());
 	if (IS_ERR(file))
 		return PTR_ERR(file);