Messages in this thread |  | | | Date | Thu, 28 Aug 2008 14:27:26 -0700 | | From | "H. Peter Anvin" <> | | Subject | Re: [PATCH 5/7] FUSE: implement ioctl support |
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Miklos Szeredi wrote: > On Thu, 28 Aug 2008, H. Peter Anvin wrote: >> This is *hard* to get right, and we screw this up in the kernel with >> painful regularity. The throught of having user-space processes, which >> don't have access to the kernel locking primitives and functions like >> copy_from_user() dealing with this stuff scares me crazy. > > What issues exactly are you thinking of?
Memory changing underneath you. It can be dealt with by very careful sequencing only.
>> That is why I'm suggesting using an in-kernel linearizer. > > Lots of complexity, ugh... Even Tejun's current scheme is better IMO.
And then you get *no* privilege separation, for one thing, so why even bother doing it in userspace?
-hpa
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