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fuse: ignore 'data' argument of mount(..., MS_REMOUNT)

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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: c30da2e981 ("fuse: convert to use the new mount API")
Cc: <stable@vger.kernel.org> # v5.4
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Miklos Szeredi 2020-07-14 14:45:41 +02:00
parent 0189a2d367
commit e8b20a474c
1 changed files with 7 additions and 0 deletions
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7
fs/fuse/inode.c
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@ -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;