On Wed, Feb 20, 2008 at 02:57:34PM +0100, Arne Georg Gleditsch wrote: > Hi, > > I'm looking at 2.6.25-rc2. vsyscall_sysctl_change contains code to NOP > out the actual system call instructions of the vsyscall page when > vsyscall64 is enabled. This seems to interact badly with the fallback > code in do_vgettimeofday which tries to call gettimeofday if the > configured clock source does not support vread. (In effect, > gettimeofday() becomes a nop and time() always returns 0. Not very > useful.) > > Is there a good reason to keep this? Aren't the instructions in > question avoided (or invoked) according to the vsyscall64 flag by the > surrounding logic anyway?
Yes they are. But a system call sequence at a known fixed address is potentially useful to exploits. That is why it is nop'ed out when it is not needed. -Andi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
