Messages in this thread | | | Date | Tue, 3 Feb 2004 08:52:24 +0000 | From | Jamie Lokier <> | Subject | Re: [RFC][PATCH] linux-2.6.2-rc2_vsyscall-gtod_B1.patch |
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Ulrich Drepper wrote: > You got to be kidding. Some object fixed in the address space which can > perform system calls. Nothing is more welcome to somebody trying to > exploit some bugs.
Two approaches to randomising the vdso address:
1. Selecting a random address at boot time. All tasks have the same vdso for that run of the kernel. Advantages: no MSR write at each context switch; could patch libsyscall.so at boot time with address if we were fanatical about optimisation (i.e. other libcs, not Glibc :) Disadvantages: the attacker may eventually learn the address.
2. Select a random address for every new task. Advantages: harder to guess from studying a machine for a long time. Disadvantages: slower context switches; the gain from randomising each task is nothing if all the tasks are very long lived anyway.
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