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bswap,xadd and cmpxchg emulation on 386



Hi *,

http://thread.gmane.org/gmane.linux.kernel/205839 has the patch. Note
that 486 stepping A processors have a wrong opcode for cmpxchg. This
means emulation of cmpxchg is necessary for 486 stepping A as well. As
to the security hole, either the patch needs some fixes (ie using get_user etc.)
or a userland emulation hooking SIGILL needs to be implemented. The
later option is probably better from a security point of view as a bug
in the emulation code only affects the current process. A bug in the
emulation code would still be an issue if setuid code uses the emulated
instructions though.

Cheers,

Peter (p2).

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