udf: Fix uninitialized array access for some pathnames

stable inclusion
from stable-v5.10.192
commit 4503f6fc95d6dee85fb2c54785848799e192c51c
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I933RF

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4503f6fc95d6dee85fb2c54785848799e192c51c



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[ Upstream commit 028f6055 ]

For filenames that begin with . and are between 2 and 5 characters long,
UDF charset conversion code would read uninitialized memory in the
output buffer. The only practical impact is that the name may be prepended a
"unification hash" when it is not actually needed but still it is good
to fix this.

Reported-by:  <syzbot+cd311b1e43cc25f90d18@syzkaller.appspotmail.com>
Link: https://lore.kernel.org/all/000000000000e2638a05fe9dc8f9@google.com


Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>