Re: [PATCH 4/7] fuse: add POSIX file locking support

[Miklos Szeredi]

> How about; on fuse startup, pick some semirandom number, store it
> somewhere, then do an XOR of the pointer with the saved value to
> scramble it, when you need to use it, simply XOR it again with the
> stored value...  Not especially strong, but better than nothing and
> better than just adding a constant that people can find out from the
> source

I think Andrew was suggesting a random key for the ADD function.

> (and the scramble value would be differene each time fuse loads, so
> at a minimum a different scramble key every boot) - also, XOR is a
> quite fast operation so overhead should be low.

I think XOR might be even weaker than ADD, because from gessing the
difference between two values (easy) you might be able to guess the
bits of the key.

I'm actually looking for something stronger than XOR or ADD, but it's
all a bit academical I think, because even if userspace knows these
kernel pointers it can't really use them for any malicious purpose.

Miklos
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