Re: [PATCH 0/3] ABI CHANGE!!! Remove questionable remote SP reads
On Mon, Oct 3, 2016 at 4:17 PM, Linus Torvalds wrote: > On Mon, Oct 3, 2016 at 4:08 PM, Andy Lutomirski wrote: >> >> Ping! >> >> We need to decide fairly soon whether to apply these (or perhaps just >> patch 1 or just patches 2 and 3) for 4.9. For any parts that aren't >> applied, I'll send quick fixups to pin the stack in the offending >> code. > > I think we should apply it. Hopefully nothing uses it, and nobody will > notice. And if somebody *does* notice, the sooner we find out, the > better. > Ingo? If we're going to make this change, I think it would be nice to do it before -rc1. If not, I want to get the alternate fix in ASAP.
Re: [PATCH 0/3] ABI CHANGE!!! Remove questionable remote SP reads
My personal opinion is that even looking at esp/rsp is asking for trouble. The only reliable information is VM_STACK or another VM flag that makes the area expand in response to stack growth. Besides, userspace could always play funky trampoline games with the stack pointer, or even dynamically expand the stack by doing a malloc if a stack overflow draws near, which would put the stack in the data section temporarily. As long as esp is in the bounds of a valid VMA, my vote is that we should consider it undefined how the task uses it. On Mon, Oct 3, 2016 at 4:17 PM, Linus Torvalds wrote: On Mon, Oct 3, 2016 at 4:08 PM, Andy Lutomirski wrote: Ping! We need to decide fairly soon whether to apply these (or perhaps just patch 1 or just patches 2 and 3) for 4.9. For any parts that aren't applied, I'll send quick fixups to pin the stack in the offending code. I think we should apply it. Hopefully nothing uses it, and nobody will notice. And if somebody *does* notice, the sooner we find out, the better. Linus
Re: [PATCH 0/3] ABI CHANGE!!! Remove questionable remote SP reads
On Mon, Oct 3, 2016 at 4:08 PM, Andy Lutomirski wrote: > > Ping! > > We need to decide fairly soon whether to apply these (or perhaps just > patch 1 or just patches 2 and 3) for 4.9. For any parts that aren't > applied, I'll send quick fixups to pin the stack in the offending > code. I think we should apply it. Hopefully nothing uses it, and nobody will notice. And if somebody *does* notice, the sooner we find out, the better. Linus
Re: [PATCH 0/3] ABI CHANGE!!! Remove questionable remote SP reads
On Fri, Sep 30, 2016 at 10:58 AM, Andy Lutomirski wrote: > Jann Horn noticed that KSTK_ESP + eager task stack freeing was a bad > combination and could crash. I could very easily fix it to not > crash, but I think that using KSTK_ESP on a remote task is > questionable in general. Therefore, I propose to get rid of the > major users for 4.9. Ping! We need to decide fairly soon whether to apply these (or perhaps just patch 1 or just patches 2 and 3) for 4.9. For any parts that aren't applied, I'll send quick fixups to pin the stack in the offending code. --Andy
