UDF reads only, and does not rewrite, by kernel.org default.
This is not a bug - this will never be closed - this is broken as
designed. I'm entering this explanation as bug only to help you
find it, because I find many newbies think this is a surprising bug.
If you want to write, you or your redistribution has to reconfigure
and rebuild your kernel.
The relevant .config override is CONFIG_UDF_RW=y. To allow that
choice, you may need CONFIG_EXPERIMENTAL=y. People say
CONFIG_UDF_FS=m sometimes works better than =y.
Linux 2.4 drags you thru this hassle by design, to defend you
against corrupting a disc by using an new filesystem that in Linux
was untried, back in such days as the 29-Jan-2001 of 2.4.1.
The Linux 2.6 begun in 2003-12 invites you to test the UDF source
code that by now is older.