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Date: Wed, 14 Oct 2015 18:09:27 +0300 From: Stas Sergeev <stsp@...t.ru> To: Ingo Molnar <mingo@...nel.org> Cc: Andy Lutomirski <luto@...nel.org>, x86@...nel.org, linux-kernel@...r.kernel.org, Brian Gerst <brgerst@...il.com>, Denys Vlasenko <dvlasenk@...hat.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Borislav Petkov <bp@...en8.de>, Cyrill Gorcunov <gorcunov@...il.com>, Pavel Emelyanov <xemul@...allels.com> Subject: Re: [RFC 3/4] x86/signal/64: Re-add support for SS in the 64-bit signal context 14.10.2015 18:01, Ingo Molnar пишет: > > * Stas Sergeev <stsp@...t.ru> wrote: > >> On an off-topic: there was recently a patch from you that >> disables vm86() by mmap_min_addr. I've found that dosemu, when >> started as root, could override mmap_min_addr. I guess this will >> no longer work, right? Not a big regression, just something to >> know and document. > > So I think it should still work, because we check for mmap_min_addr in the system > call itself: > > static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus) > { > ... > err = security_mmap_addr(0); > if (err) { > /* > > So if dosemu first tweaks mmap_min_addr, the syscall should succeed. No, it doesn't tweak it. It just seems that root is allowed to do mmap(0, MAP_FIXED) _regardless_ of mmap_min_addr. But it would be crazy to run vm86() as root to also bypass the check (dosemu drops privs earlier), so I guess this trick will stop working. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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