Bugtraq mailing list archives
Re: Solaris 7 x86 lpset exploit.
From: mouse () RODENTS MONTREAL QC CA (der Mouse)
Date: Wed, 3 May 2000 02:04:44 -0400
Another possible way around it would be to cause gcc to keep part of the stack in the data segment, out of what the kernel thinks of as the stack, and have it do its trampolines there. This runs into big problems with setjmp and other nonlocal exits, and possibly with signal handlers as well.
You could handle that by having a frame pointer on the processor stack point into the function's executable stack frame (if it has one) on the trampoline stack, rather than having a permanent stack pointer into this space. I don't think there would be any issues with this, unless you're trying to use setjmp/longjmp for coroutines or something perverse like that.
If you longjmp out, how do you free up the jumped-through frames on the executable stack? If you do it by using a contiguous executable stack with an offset-style pointer into it, conceptually the way longjmp deals with freeing ordinary stack frames, how do you deal with overflow, without wasting large amounts of data segment space on programs that don't need deep executable stacks? If you do it with a linked list of frame structures, how do you push frames on it without risking either a corrupted stack or a lost frame in the presence of longjmp out of a signal handler? If you do it with something else, well, what? Someone else said - I don't have the quote handy - that modern gcc calls mprotect() after setting up a trampoline. The notion of doing a *syscall* per entry to a routine that uses trampolines, even when the system may not need it (may have the stack executable already), that makes me shudder. I trust this can be turned off at compile time? I'd really hate to have to dummy out mprotect() just to get minimally sane call performance. (Oh, and what gcc version is that?) der Mouse mouse () rodents montreal qc ca 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B
Current thread:
- Re: Solaris 7 x86 lpset exploit. Casper Dik (May 01)
- <Possible follow-ups>
- Re: Solaris 7 x86 lpset exploit. Peter da Silva (May 01)
- Re: Solaris 7 x86 lpset exploit. der Mouse (May 02)
- Re: Solaris 7 x86 lpset exploit. Casper Dik (May 03)
- Passive Network Mapping bind (May 04)
- Re: Solaris 7 x86 lpset exploit. Peter da Silva (May 04)