From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f199.google.com (mail-pf1-f199.google.com [209.85.210.199]) by kanga.kvack.org (Postfix) with ESMTP id 1CFF66B38E4 for ; Sun, 26 Aug 2018 00:21:46 -0400 (EDT) Received: by mail-pf1-f199.google.com with SMTP id x19-v6so9151439pfh.15 for ; Sat, 25 Aug 2018 21:21:46 -0700 (PDT) Received: from mail.kernel.org (mail.kernel.org. [198.145.29.99]) by mx.google.com with ESMTPS id 11-v6si10740279plc.154.2018.08.25.21.21.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 25 Aug 2018 21:21:45 -0700 (PDT) Received: from mail-wm0-f49.google.com (mail-wm0-f49.google.com [74.125.82.49]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 40C5D21756 for ; Sun, 26 Aug 2018 04:21:44 +0000 (UTC) Received: by mail-wm0-f49.google.com with SMTP id j192-v6so5147979wmj.1 for ; Sat, 25 Aug 2018 21:21:44 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20180826112341.f77a528763e297cbc36058fa@kernel.org> References: <20180822153012.173508681@infradead.org> <20180822154046.823850812@infradead.org> <20180822155527.GF24124@hirez.programming.kicks-ass.net> <20180823134525.5f12b0d3@roar.ozlabs.ibm.com> <776104d4c8e4fc680004d69e3a4c2594b638b6d1.camel@au1.ibm.com> <20180823133958.GA1496@brain-police> <20180824084717.GK24124@hirez.programming.kicks-ass.net> <20180824180438.GS24124@hirez.programming.kicks-ass.net> <56A9902F-44BE-4520-A17C-26650FCC3A11@gmail.com> <9A38D3F4-2F75-401D-8B4D-83A844C9061B@gmail.com> <8E0D8C66-6F21-4890-8984-B6B3082D4CC5@gmail.com> <20180826112341.f77a528763e297cbc36058fa@kernel.org> From: Andy Lutomirski Date: Sat, 25 Aug 2018 21:21:22 -0700 Message-ID: Subject: Re: TLB flushes on fixmap changes Content-Type: multipart/mixed; boundary="00000000000028b5cb05744ef28c" Sender: owner-linux-mm@kvack.org List-ID: To: Masami Hiramatsu , Kees Cook Cc: Andy Lutomirski , Nadav Amit , Linus Torvalds , Paolo Bonzini , Jiri Kosina , Peter Zijlstra , Will Deacon , Benjamin Herrenschmidt , Nick Piggin , the arch/x86 maintainers , Borislav Petkov , Rik van Riel , Jann Horn , Adin Scannell , Dave Hansen , Linux Kernel Mailing List , linux-mm , David Miller , Martin Schwidefsky , Michael Ellerman --00000000000028b5cb05744ef28c Content-Type: text/plain; charset="UTF-8" On Sat, Aug 25, 2018 at 7:23 PM, Masami Hiramatsu wrote: > On Fri, 24 Aug 2018 21:23:26 -0700 > Andy Lutomirski wrote: >> Couldn't text_poke() use kmap_atomic()? Or, even better, just change CR3? > > No, since kmap_atomic() is only for x86_32 and highmem support kernel. > In x86-64, it seems that returns just a page address. That is not > good for text_poke, since it needs to make a writable alias for RO > code page. Hmm, maybe, can we mimic copy_oldmem_page(), it uses ioremap_cache? > I just re-read text_poke(). It's, um, horrible. Not only is the implementation overcomplicated and probably buggy, but it's SLOOOOOW. It's totally the wrong API -- poking one instruction at a time basically can't be efficient on x86. The API should either poke lots of instructions at once or should be text_poke_begin(); ...; text_poke_end();. Anyway, the attached patch seems to boot. Linus, Kees, etc: is this too scary of an approach? With the patch applied, text_poke() is a fantastic exploit target. On the other hand, even without the patch applied, text_poke() is every bit as juicy. --Andy --00000000000028b5cb05744ef28c Content-Type: text/x-patch; charset="US-ASCII"; name="text_poke.patch" Content-Disposition: attachment; filename="text_poke.patch" Content-Transfer-Encoding: base64 X-Attachment-Id: f_jlacjmnk0 ZGlmZiAtLWdpdCBhL2FyY2gveDg2L2tlcm5lbC9hbHRlcm5hdGl2ZS5jIGIvYXJjaC94ODYva2Vy bmVsL2FsdGVybmF0aXZlLmMKaW5kZXggMDE0ZjIxNGRhNTgxLi44MTFjODczNWIxMjkgMTAwNjQ0 Ci0tLSBhL2FyY2gveDg2L2tlcm5lbC9hbHRlcm5hdGl2ZS5jCisrKyBiL2FyY2gveDg2L2tlcm5l bC9hbHRlcm5hdGl2ZS5jCkBAIC02OTAsNDAgKzY5MCwxNSBAQCB2b2lkICpfX2luaXRfb3JfbW9k dWxlIHRleHRfcG9rZV9lYXJseSh2b2lkICphZGRyLCBjb25zdCB2b2lkICpvcGNvZGUsCiB2b2lk ICp0ZXh0X3Bva2Uodm9pZCAqYWRkciwgY29uc3Qgdm9pZCAqb3Bjb2RlLCBzaXplX3QgbGVuKQog ewogCXVuc2lnbmVkIGxvbmcgZmxhZ3M7Ci0JY2hhciAqdmFkZHI7Ci0Jc3RydWN0IHBhZ2UgKnBh Z2VzWzJdOwotCWludCBpOwotCi0JLyoKLQkgKiBXaGlsZSBib290IG1lbW9yeSBhbGxvY2F0b3Ig aXMgcnVubmlnIHdlIGNhbm5vdCB1c2Ugc3RydWN0Ci0JICogcGFnZXMgYXMgdGhleSBhcmUgbm90 IHlldCBpbml0aWFsaXplZC4KLQkgKi8KLQlCVUdfT04oIWFmdGVyX2Jvb3RtZW0pOworCXVuc2ln bmVkIGxvbmcgb2xkX2NyMDsKIAotCWlmICghY29yZV9rZXJuZWxfdGV4dCgodW5zaWduZWQgbG9u ZylhZGRyKSkgewotCQlwYWdlc1swXSA9IHZtYWxsb2NfdG9fcGFnZShhZGRyKTsKLQkJcGFnZXNb MV0gPSB2bWFsbG9jX3RvX3BhZ2UoYWRkciArIFBBR0VfU0laRSk7Ci0JfSBlbHNlIHsKLQkJcGFn ZXNbMF0gPSB2aXJ0X3RvX3BhZ2UoYWRkcik7Ci0JCVdBUk5fT04oIVBhZ2VSZXNlcnZlZChwYWdl c1swXSkpOwotCQlwYWdlc1sxXSA9IHZpcnRfdG9fcGFnZShhZGRyICsgUEFHRV9TSVpFKTsKLQl9 Ci0JQlVHX09OKCFwYWdlc1swXSk7CiAJbG9jYWxfaXJxX3NhdmUoZmxhZ3MpOwotCXNldF9maXht YXAoRklYX1RFWFRfUE9LRTAsIHBhZ2VfdG9fcGh5cyhwYWdlc1swXSkpOwotCWlmIChwYWdlc1sx XSkKLQkJc2V0X2ZpeG1hcChGSVhfVEVYVF9QT0tFMSwgcGFnZV90b19waHlzKHBhZ2VzWzFdKSk7 Ci0JdmFkZHIgPSAoY2hhciAqKWZpeF90b192aXJ0KEZJWF9URVhUX1BPS0UwKTsKLQltZW1jcHko JnZhZGRyWyh1bnNpZ25lZCBsb25nKWFkZHIgJiB+UEFHRV9NQVNLXSwgb3Bjb2RlLCBsZW4pOwot CWNsZWFyX2ZpeG1hcChGSVhfVEVYVF9QT0tFMCk7Ci0JaWYgKHBhZ2VzWzFdKQotCQljbGVhcl9m aXhtYXAoRklYX1RFWFRfUE9LRTEpOwotCWxvY2FsX2ZsdXNoX3RsYigpOwotCXN5bmNfY29yZSgp OwotCS8qIENvdWxkIGFsc28gZG8gYSBDTEZMVVNIIGhlcmUgdG8gc3BlZWQgdXAgQ1BVIHJlY292 ZXJ5OyBidXQKLQkgICB0aGF0IGNhdXNlcyBoYW5ncyBvbiBzb21lIFZJQSBDUFVzLiAqLwotCWZv ciAoaSA9IDA7IGkgPCBsZW47IGkrKykKLQkJQlVHX09OKCgoY2hhciAqKWFkZHIpW2ldICE9ICgo Y2hhciAqKW9wY29kZSlbaV0pOworCW9sZF9jcjAgPSByZWFkX2NyMCgpOworCXdyaXRlX2NyMChv bGRfY3IwICYgflg4Nl9DUjBfV1ApOworCisJbWVtY3B5KGFkZHIsIG9wY29kZSwgbGVuKTsKKwor CXdyaXRlX2NyMChvbGRfY3IwKTsJLyogYWxzbyBzZXJpYWxpemVzICovCiAJbG9jYWxfaXJxX3Jl c3RvcmUoZmxhZ3MpOwogCXJldHVybiBhZGRyOwogfQo= --00000000000028b5cb05744ef28c--