linux-kernel - [PATCH 44/52] fuse: Clear setuid bit even in direct I/O path

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Date:   Mon, 10 Dec 2018 12:13:10 -0500
From:   Vivek Goyal <vgoyal@...hat.com>
To:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     vgoyal@...hat.com, miklos@...redi.hu, stefanha@...hat.com,
        dgilbert@...hat.com, sweil@...hat.com, swhiteho@...hat.com
Subject: [PATCH 44/52] fuse: Clear setuid bit even in direct I/O path

With cache=never, we fall back to direct IO. pjdfstest chmod test 12.t was
failing because if a file has setuid bit, it should be cleared if an
unpriviledged user opens it for write and writes to it.

Call fuse_remove_privs() even for direct I/O path.

Signed-off-by: Vivek Goyal <vgoyal@...hat.com>
---
 fs/fuse/file.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index cb28cf26a6e7..0be5a7380b3c 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1679,13 +1679,25 @@ static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	/* Don't allow parallel writes to the same file */
 	inode_lock(inode);
 	res = generic_write_checks(iocb, from);
-	if (res > 0)
-		res = fuse_direct_io(&io, from, &iocb->ki_pos, FUSE_DIO_WRITE);
+	if (res < 0)
+		goto out_invalidate;
+
+	res = file_remove_privs(iocb->ki_filp);
+	if (res)
+		goto out_invalidate;
+
+	res = fuse_direct_io(&io, from, &iocb->ki_pos, FUSE_DIO_WRITE);
+	if (res < 0)
+		goto out_invalidate;
+
 	fuse_invalidate_attr(inode);
-	if (res > 0)
-		fuse_write_update_size(inode, iocb->ki_pos);
+	fuse_write_update_size(inode, iocb->ki_pos);
 	inode_unlock(inode);
+	return res;
 
+out_invalidate:
+	fuse_invalidate_attr(inode);
+	inode_unlock(inode);
 	return res;
 }
 
-- 
2.13.6