linux-kernel - [PATCH] ovl: properly handle large files in ovl_security

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Message-ID: <20241030002856.2103752-1-ovt@google.com>
Date: Wed, 30 Oct 2024 00:28:55 +0000
From: Oleksandr Tymoshenko <ovt@...gle.com>
To: Miklos Szeredi <miklos@...redi.hu>, Amir Goldstein <amir73il@...il.com>
Cc: ovt@...gle.com, stable@...r.kernel.org, 
	Miklos Szeredi <mszeredi@...hat.com>, linux-unionfs@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH] 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@...gle.com>
Fixes: 72db82115d2b ("ovl: copy up sync/noatime fileattr flags")
Cc: stable@...r.kernel.org # v5.15+
---
 fs/overlayfs/inode.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 35fd3e3e1778..baa54c718bd7 100644
--- a/fs/overlayfs/inode.c
+++ b/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);
 
-- 
2.47.0.163.g1226f6d8fa-goog