On Thursday 22 June 2006 23:06, Willy Tarreau wrote:
>
> I've been reported by the PaX Team that the following fix left a
> small hole :
>
> [PATCH] Always check that RIPs are canonical during signal handling
>
> + if (regs->rip >= TASK_SIZE && regs->rip < VSYSCALL_START) {
> + regs->rip = 0;
> + return -EFAULT;
> + }
>
> ...
>
> + if (regs->rip >= TASK_SIZE) {
> + if (sig == SIGSEGV)
> + ka->sa.sa_handler = SIG_DFL;
> + regs->rip = 0;
> + }
>
> "the wrong part is regs->rip=0, i guess the intention was to cause a
> SIGSEGV upon returning to userland, but 0 is a valid userland address,
> an application may very well have something mapped there. the correct
> value would be ~0UL as it's guaranteed to fault on linux."
>
> This explanation makes sense, so here's the patch. Andi, would you please
> review and confirm ? Thanks in advance.
I don't think it's a real problem.
The patch is not wrong, but also doesn't fix something that needs
to be fixed.
-Andi
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