Fwd: [oss-security] "I miss LSD", slides, paper and tools relating to finding UNIX system level vulnerabilities (as given at 44CON)
Mouse
mouse at Rodents-Montreal.ORG
Thu Nov 14 23:16:19 PST 2013
> My understanding is that the new code, by passing shared memory
> through fd is a lot better since [...]
In those respects, yes. But it's worse in that it requires write
access to a filesystem - a filesystem which supports mmap - with space
enough to hold the shared memory segments, which MIT-SHM doesn't.
Tradeoffs, tradeoffs....
> it doesn't rely on file system permissions to control access,
Neither does MIT-SHM, I thought. I thought it relied on shared memory
segment permissions (which in some respects look and work like
filesystem permissions, but actually have nothing to do with any
filesystem).
What I think this _really_ needs is either a way to pass access to a
chunk of memory through sockets a la SCM_RIGHTS, or a way to create a
file descriptor which is mmappable but doesn't depend on anything in
any filesystem. (I'd prefer the former; after all, "access rights"
covers a lot more than file descriptors - and I've wished for it often
enough before; it would hardly be specific to this application.)
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