Re: Symlink attack vulnerability in auto-saving

[Davis Herring]

> Following the recent discussion about symlinks and race-conditions in
> the thread "creating backups in temporary directories", I may have
> discovered a more severe vulnerability in auto-saving of files.  If a
> file foobar exists, Emacs will write auto-save data to #foobar# and
> follow symlinks.  That's rather bad if foobar is in a world-writable
> directory. :-(

Just to put the message on all threads, in case it's deemed the correct
answer, O_EXCL can work here, too, with the same trick of renaming an old
(non-malicious) auto-save file to reduce the amount of time that no useful
auto-save data is on disk.

Davis

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