On Thu, Feb 21, 2008 at 08:45:53PM +0100, Thomas Gleixner wrote: > On Thu, 21 Feb 2008, Andi Kleen wrote: > > > 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. > > That's a nice intent, but the reality is that this code is broken as > hell:
Well it worked when I wrote it, but it's quite possible it didn't survive the clocksource conversion completely. -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/
