[PATCH 1/3] fuse: use ->reconfigure() instead of ->remount_fs()

[PATCH 1/3] fuse: use ->reconfigure() instead of ->remount_fs()

[Miklos Szeredi]

s_op->remount_fs() is only called from legacy_reconfigure(), which is not
used after being converted to the new API.

Convert to using ->reconfigure().  This restores the previous behavior of
syncing the filesystem and rejecting MS_MANDLOCK on remount.

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 | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 5b4aebf5821f..be39dff57c28 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -121,10 +121,12 @@ static void fuse_evict_inode(struct inode *inode)
 	}
 }
 
-static int fuse_remount_fs(struct super_block *sb, int *flags, char *data)
+static int fuse_reconfigure(struct fs_context *fc)
 {
+	struct super_block *sb = fc->root->d_sb;
+
 	sync_filesystem(sb);
-	if (*flags & SB_MANDLOCK)
+	if (fc->sb_flags & SB_MANDLOCK)
 		return -EINVAL;
 
 	return 0;
@@ -817,7 +819,6 @@ static const struct super_operations fuse_super_operations = {
 	.evict_inode	= fuse_evict_inode,
 	.write_inode	= fuse_write_inode,
 	.drop_inode	= generic_delete_inode,
-	.remount_fs	= fuse_remount_fs,
 	.put_super	= fuse_put_super,
 	.umount_begin	= fuse_umount_begin,
 	.statfs		= fuse_statfs,
@@ -1296,6 +1297,7 @@ static int fuse_get_tree(struct fs_context *fc)
 static const struct fs_context_operations fuse_context_ops = {
 	.free		= fuse_free_fc,
 	.parse_param	= fuse_parse_param,
+	.reconfigure	= fuse_reconfigure,
 	.get_tree	= fuse_get_tree,
 };
 
-- 
2.21.1

[PATCH 2/3] fuse: ignore 'data' argument of mount(..., MS_REMOUNT)

[Miklos Szeredi]

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

Re: [PATCH 2/3] fuse: ignore 'data' argument of mount(..., MS_REMOUNT)

[Sasha Levin]

Hi

[This is an automated email]

This commit has been processed because it contains a "Fixes:" tag
fixing commit: c30da2e981a7 ("fuse: convert to use the new mount API").

The bot has tested the following trees: v5.7.8, v5.4.51.

v5.7.8: Build OK!
v5.4.51: Failed to apply! Possible dependencies:
    7f5d38141e309 ("new primitive: __fs_parse()")
    82995cc6c5ae4 ("libceph, rbd, ceph: convert to use the new mount API")
    d7167b149943e ("fs_parse: fold fs_parameter_desc/fs_parameter_spec")


NOTE: The patch will not be queued to stable trees until it is upstream.

How should we proceed with this patch?

-- 
Thanks
Sasha

Re: [PATCH 2/3] fuse: ignore 'data' argument of mount(..., MS_REMOUNT)

[Miklos Szeredi]

[-- Attachment #1: Type: text/plain, Size: 764 bytes --]

On Thu, Jul 16, 2020 at 2:27 AM Sasha Levin <sashal@kernel.org> wrote:
>
> Hi
>
> [This is an automated email]
>
> This commit has been processed because it contains a "Fixes:" tag
> fixing commit: c30da2e981a7 ("fuse: convert to use the new mount API").
>
> The bot has tested the following trees: v5.7.8, v5.4.51.
>
> v5.7.8: Build OK!
> v5.4.51: Failed to apply! Possible dependencies:
>     7f5d38141e309 ("new primitive: __fs_parse()")
>     82995cc6c5ae4 ("libceph, rbd, ceph: convert to use the new mount API")
>     d7167b149943e ("fs_parse: fold fs_parameter_desc/fs_parameter_spec")
>
>
> NOTE: The patch will not be queued to stable trees until it is upstream.
>
> How should we proceed with this patch?

Conflict resolution is trivial.

Thanks,
Miklos

[-- Attachment #2: merge.patch --]
[-- Type: text/x-patch, Size: 570 bytes --]

diff --cc fs/fuse/inode.c
index 16aec32f7f3d,ba201bf5ffad..000000000000
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@@ -473,7 -477,14 +473,14 @@@ static int fuse_parse_param(struct fs_c
  	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);
 +	opt = fs_parse(fc, &fuse_fs_parameters, param, &result);
  	if (opt < 0)
  		return opt;