On 2023-06-07 21:39:01+0200, Christian Brauner wrote: > On Wed, Jun 07, 2023 at 07:28:48PM +0200, Thomas Weißschuh wrote: > > As each option string fragment is always prepended with a comma it would > > happen that the whole string always starts with a comma. > > This could be interpreted by filesystem drivers as an empty option and > > may produce errors. > > > > For example the NTFS driver from ntfs.ko behaves like this and fails when > > mounted via the new API. > > > > Link: https://github.com/util-linux/util-linux/issues/2298 > > Yeah, the old ntfs driver implements its own option parser. It > overwrites/splits at ',' returning '\0' and then trips over this. > > Contrast with e.g., ovl_next_op() which does the same thing but skips > over '\0' in ovl_parse_opt(). > > So arguably also a bug in ntfs parsing. But there's no reason we should > prepend ',' for legacy mount option strings. > > And yeah, I can easily verify this... > > Using my custom move-mount tool I originally wrote for another patchset > but which is handy to pass mount options via the new mount api _system_ > calls and not via mount(): > https://github.com/brauner/move-mount-beneath > > I can do: > > sudo ./move-mount -f overlay -olowerdir=/mnt/a:/mnt/b,upperdir=/mnt/upper,workdir=/mnt/work /mnt/merged > > and clearly see: > > > sudo bpftrace -e 'kfunc:legacy_get_tree { @m = args->fc; printf("%s\n", str(((struct legacy_fs_context *)@m->fs_private)->legacy_data)); }' > Attaching 1 probe... > ,lowerdir=/mnt/a:/mnt/b,upperdir=/mnt/upper,workdir=/mnt/work > > > Fixes: 3e1aeb00e6d1 ("vfs: Implement a filesystem superblock creation/configuration context") > > Should be: > > Fixes: commit 3e1aeb00e6d1 ("vfs: Implement a filesystem superblock creation/configuration context") AFAIK the Fixes: tag does not use the "commit" keyword. Only inline commit references. This is how it's currently documented in Documentation/process/submitting-patches.rst. > and misses a: > > Cc: stable@xxxxxxxxxxxxxxx This was fixed in v2. > I'll fix this up for you though. Thanks! Thomas
