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@xxxxxxxxxxxx>
Fixes: c30da2e981a7 ("fuse: convert to use the new mount API")
Cc: <stable@xxxxxxxxxxxxxxx> # v5.4
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
---
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
