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From: Miklos Szeredi <mszeredi@redhat.com>
To: linux-fsdevel@vger.kernel.org
Cc: Stefan Priebe <s.priebe@profihost.ag>,
	David Howells <dhowells@redhat.com>,
	stable@vger.kernel.org
Subject: [PATCH 2/3] fuse: ignore 'data' argument of mount(..., MS_REMOUNT)
Date: Fri, 10 Jul 2020 13:58:04 +0200	[thread overview]
Message-ID: <20200710115805.4478-2-mszeredi@redhat.com> (raw)
In-Reply-To: <20200710115805.4478-1-mszeredi@redhat.com>

The command

  mount -o remount -o unknownoption /mnt/fuse

succeeds on kernel versions prior to v5.4 and fails on kernel version at or
after.  This is because fuse_parse_param() rejects any unrecognised options
in case of FS_CONTEXT_FOR_RECONFIGURE, just as for FS_CONTEXT_FOR_MOUNT.

This causes a regression in case the fuse filesystem is in fstab, since
remount sends all options found there to the kernel; even ones that are
meant for the initial mount and are consumed by the userspace fuse server.

Fix this by ignoring mount options, just as fuse_remount_fs() did prior to
the conversion to the new API.

Reported-by: Stefan Priebe <s.priebe@profihost.ag>
Fixes: c30da2e981a7 ("fuse: convert to use the new mount API")
Cc: <stable@vger.kernel.org> # v5.4
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
 fs/fuse/inode.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index be39dff57c28..ba201bf5ffad 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -477,6 +477,13 @@ static int fuse_parse_param(struct fs_context *fc, struct fs_parameter *param)
 	struct fuse_fs_context *ctx = fc->fs_private;
 	int opt;
 
+	/*
+	 * Ignore options coming from mount(MS_REMOUNT) for backward
+	 * compatibility.
+	 */
+	if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE)
+		return 0;
+
 	opt = fs_parse(fc, fuse_fs_parameters, param, &result);
 	if (opt < 0)
 		return opt;
-- 
2.21.1


  reply	other threads:[~2020-07-10 11:58 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-10 11:58 [PATCH 1/3] fuse: use ->reconfigure() instead of ->remount_fs() Miklos Szeredi
2020-07-10 11:58 ` Miklos Szeredi [this message]
2020-07-16  0:27   ` [PATCH 2/3] fuse: ignore 'data' argument of mount(..., MS_REMOUNT) Sasha Levin
2020-07-20  9:14     ` Miklos Szeredi
2020-07-10 11:58 ` [PATCH 3/3] fuse: reject options on reconfigure via fsconfig(2) Miklos Szeredi

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