[PATCH 2/2] ovl: remove privs in ovl_fallocate()

From: Amir Goldstein <amir73il@gmail.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Christian Brauner <brauner@kernel.com>,
	Yang Xu <xuyang2018.jy@fujitsu.com>,
	"Darrick J . Wong" <djwong@kernel.org>,
	Filipe Manana <fdmanana@kernel.org>,
	linux-unionfs@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: [PATCH 2/2] ovl: remove privs in ovl_fallocate()
Date: Mon,  3 Oct 2022 15:21:54 +0300	[thread overview]
Message-ID: <20221003122154.900300-3-amir73il@gmail.com> (raw)
In-Reply-To: <20221003122154.900300-1-amir73il@gmail.com>

Underlying fs doesn't remove privs because fallocate is called with
privileged mounter credentials.

This fixes some failure in fstests generic/683..687.

Fixes: aab8848cee5e ("ovl: add ovl_fallocate()")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/overlayfs/file.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index c8308da8909a..e90ac5376456 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -517,9 +517,16 @@ static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len
 	const struct cred *old_cred;
 	int ret;
 
+	inode_lock(inode);
+	/* Update mode */
+	ovl_copyattr(inode);
+	ret = file_remove_privs(file);
+	if (ret)
+		goto out_unlock;
+
 	ret = ovl_real_fdget(file, &real);
 	if (ret)
-		return ret;
+		goto out_unlock;
 
 	old_cred = ovl_override_creds(file_inode(file)->i_sb);
 	ret = vfs_fallocate(real.file, mode, offset, len);
@@ -530,6 +537,9 @@ static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len
 
 	fdput(real);
 
+out_unlock:
+	inode_unlock(inode);
+
 	return ret;
 }
 
-- 
2.25.1

