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Wed, 8 Apr 2020 10:42:51 +0000 (UTC) Subject: Re: [PATCH 05/13] efi/x86: don't map the entire kernel text RW for mixed mode To: Ard Biesheuvel , linux-efi@vger.kernel.org, Ingo Molnar , Thomas Gleixner Cc: linux-kernel@vger.kernel.org, Anshuman Khandual , Arnd Bergmann , Dan Williams , Dave Young , Saravana Kannan References: <20200113172245.27925-1-ardb@kernel.org> <20200113172245.27925-6-ardb@kernel.org> From: Jiri Slaby Autocrypt: addr=jslaby@suse.cz; prefer-encrypt=mutual; keydata= mQINBE6S54YBEACzzjLwDUbU5elY4GTg/NdotjA0jyyJtYI86wdKraekbNE0bC4zV+ryvH4j rrcDwGs6tFVrAHvdHeIdI07s1iIx5R/ndcHwt4fvI8CL5PzPmn5J+h0WERR5rFprRh6axhOk rSD5CwQl19fm4AJCS6A9GJtOoiLpWn2/IbogPc71jQVrupZYYx51rAaHZ0D2KYK/uhfc6neJ i0WqPlbtIlIrpvWxckucNu6ZwXjFY0f3qIRg3Vqh5QxPkojGsq9tXVFVLEkSVz6FoqCHrUTx wr+aw6qqQVgvT/McQtsI0S66uIkQjzPUrgAEtWUv76rM4ekqL9stHyvTGw0Fjsualwb0Gwdx ReTZzMgheAyoy/umIOKrSEpWouVoBt5FFSZUyjuDdlPPYyPav+hpI6ggmCTld3u2hyiHji2H cDpcLM2LMhlHBipu80s9anNeZhCANDhbC5E+NZmuwgzHBcan8WC7xsPXPaiZSIm7TKaVoOcL 9tE5aN3jQmIlrT7ZUX52Ff/hSdx/JKDP3YMNtt4B0cH6ejIjtqTd+Ge8sSttsnNM0CQUkXps w98jwz+Lxw/bKMr3NSnnFpUZaxwji3BC9vYyxKMAwNelBCHEgS/OAa3EJoTfuYOK6wT6nadm YqYjwYbZE5V/SwzMbpWu7Jwlvuwyfo5mh7w5iMfnZE+vHFwp/wARAQABtBtKaXJpIFNsYWJ5 IDxqc2xhYnlAc3VzZS5jej6JAjgEEwECACIFAk6S6NgCGwMGCwkIBwMCBhUIAgkKCwQWAgMB Ah4BAheAAAoJEL0lsQQGtHBJgDsP/j9wh0vzWXsOPO3rDpHjeC3BT5DKwjVN/KtP7uZttlkB duReCYMTZGzSrmK27QhCflZ7Tw0Naq4FtmQSH8dkqVFugirhlCOGSnDYiZAAubjTrNLTqf7e 5poQxE8mmniH/Asg4KufD9bpxSIi7gYIzaY3hqvYbVF1vYwaMTujojlixvesf0AFlE4x8WKs wpk43fmo0ZLcwObTnC3Hl1JBsPujCVY8t4E7zmLm7kOB+8EHaHiRZ4fFDWweuTzRDIJtVmrH LWvRDAYg+IH3SoxtdJe28xD9KoJw4jOX1URuzIU6dklQAnsKVqxz/rpp1+UVV6Ky6OBEFuoR 613qxHCFuPbkRdpKmHyE0UzmniJgMif3v0zm/+1A/VIxpyN74cgwxjhxhj/XZWN/LnFuER1W zTHcwaQNjq/I62AiPec5KgxtDeV+VllpKmFOtJ194nm9QM9oDSRBMzrG/2AY/6GgOdZ0+qe+ 4BpXyt8TmqkWHIsVpE7I5zVDgKE/YTyhDuqYUaWMoI19bUlBBUQfdgdgSKRMJX4vE72dl8BZ +/ONKWECTQ0hYntShkmdczcUEsWjtIwZvFOqgGDbev46skyakWyod6vSbOJtEHmEq04NegUD al3W7Y/FKSO8NqcfrsRNFWHZ3bZ2Q5X0tR6fc6gnZkNEtOm5fcWLY+NVz4HLaKrJuQINBE6S 54YBEADPnA1iy/lr3PXC4QNjl2f4DJruzW2Co37YdVMjrgXeXpiDvneEXxTNNlxUyLeDMcIQ K8obCkEHAOIkDZXZG8nr4mKzyloy040V0+XA9paVs6/ice5l+yJ1eSTs9UKvj/pyVmCAY1Co SNN7sfPaefAmIpduGacp9heXF+1Pop2PJSSAcCzwZ3PWdAJ/w1Z1Dg/tMCHGFZ2QCg4iFzg5 Bqk4N34WcG24vigIbRzxTNnxsNlU1H+tiB81fngUp2pszzgXNV7CWCkaNxRzXi7kvH+MFHu2 1m/TuujzxSv0ZHqjV+mpJBQX/VX62da0xCgMidrqn9RCNaJWJxDZOPtNCAWvgWrxkPFFvXRl t52z637jleVFL257EkMI+u6UnawUKopa+Tf+R/c+1Qg0NHYbiTbbw0pU39olBQaoJN7JpZ99 T1GIlT6zD9FeI2tIvarTv0wdNa0308l00bas+d6juXRrGIpYiTuWlJofLMFaaLYCuP+e4d8x rGlzvTxoJ5wHanilSE2hUy2NSEoPj7W+CqJYojo6wTJkFEiVbZFFzKwjAnrjwxh6O9/V3O+Z XB5RrjN8hAf/4bSo8qa2y3i39cuMT8k3nhec4P9M7UWTSmYnIBJsclDQRx5wSh0Mc9Y/psx9 B42WbV4xrtiiydfBtO6tH6c9mT5Ng+d1sN/VTSPyfQARAQABiQIfBBgBAgAJBQJOkueGAhsM AAoJEL0lsQQGtHBJN7UQAIDvgxaW8iGuEZZ36XFtewH56WYvVUefs6+Pep9ox/9ZXcETv0vk DUgPKnQAajG/ViOATWqADYHINAEuNvTKtLWmlipAI5JBgE+5g9UOT4i69OmP/is3a/dHlFZ3 qjNk1EEGyvioeycJhla0RjakKw5PoETbypxsBTXk5EyrSdD/I2Hez9YGW/RcI/WC8Y4Z/7FS ITZhASwaCOzy/vX2yC6iTx4AMFt+a6Z6uH/xGE8pG5NbGtd02r+m7SfuEDoG3Hs1iMGecPyV XxCVvSV6dwRQFc0UOZ1a6ywwCWfGOYqFnJvfSbUiCMV8bfRSWhnNQYLIuSv/nckyi8CzCYIg c21cfBvnwiSfWLZTTj1oWyj5a0PPgGOdgGoIvVjYXul3yXYeYOqbYjiC5t99JpEeIFupxIGV ciMk6t3pDrq7n7Vi/faqT+c4vnjazJi0UMfYnnAzYBa9+NkfW0w5W9Uy7kW/v7SffH/2yFiK 9HKkJqkN9xYEYaxtfl5pelF8idoxMZpTvCZY7jhnl2IemZCBMs6s338wS12Qro5WEAxV6cjD VSdmcD5l9plhKGLmgVNCTe8DPv81oDn9s0cIRLg9wNnDtj8aIiH8lBHwfUkpn32iv0uMV6Ae sLxhDWfOR4N+wu1gzXWgLel4drkCJcuYK5IL1qaZDcuGR8RPo3jbFO7Y Message-ID: <63b125a4-6c62-fcdf-de22-d3bebe2dcbf5@suse.cz> Date: Wed, 8 Apr 2020 12:42:50 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200113172245.27925-6-ardb@kernel.org> Content-Type: text/plain; charset=iso-8859-2 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13. 01. 20, 18:22, Ard Biesheuvel wrote: > The mixed mode thunking routine requires a part of it to be > mapped 1:1, and for this reason, we currently map the entire > kernel .text read/write in the EFI page tables, which is bad. > > In fact, the kernel_map_pages_in_pgd() invocation that installs > this mapping is entirely redundant, since all of DRAM is already > 1:1 mapped read/write in the EFI page tables when we reach this > point, which means that .rodata is mapped read-write as well. > > So let's remap both .text and .rodata read-only in the EFI > page tables. This patch causes unhandled page faults in mixed mode: > BUG: unable to handle page fault for address: 000000001557ee88 > #PF: supervisor write access in kernel mode > #PF: error_code(0x0003) - permissions violation > PGD fd52063 P4D fd52063 PUD fd53063 PMD 154000e1 > Oops: 0003 [#1] SMP PTI > CPU: 1 PID: 191 Comm: systemd-escape Not tainted 5.6.2-20.gb22bc26-default #1 openSUSE Tumbleweed (unreleased) > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015 > RIP: 0008:0x3d2eed95 > Code: 8b 45 d4 8b 4d 10 8b 40 04 89 01 89 3b 50 6a 00 8b 55 0c 6a 00 8b 45 08 0f b6 4d e4 6a 01 31 f6 e8 ee c5 fc ff 83 c4 10 eb 07 <89> 03 be 05 00 00 80 a1 74 63 31 3d 83 c0 48 e8 44 d2 ff ff eb 05 > RSP: 0018:000000000fd66fa0 EFLAGS: 00010002 > RAX: 0000000000000001 RBX: 000000001557ee88 RCX: 000000003d1f1120 > RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000001 > RBP: 000000000fd66fd8 R08: 000000001557ee88 R09: 0000000000000000 > R10: 0000000000000055 R11: 0000000000000000 R12: 0000000015bcf000 > R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 > FS: 00007f36ee9dc940(0000) GS:ffff9b903d700000(0000) knlGS:0000000000000000 > CS: 0008 DS: 0018 ES: 0018 CR0: 0000000080050033 > CR2: 000000001557ee88 CR3: 000000000fd5e000 CR4: 00000000000006e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > Modules linked in: efivarfs > CR2: 000000001557ee88 EFI apparently tries to write to now read-only memory. See: https://bugzilla.suse.com/show_bug.cgi?id=1168645 Reverting it on the top of 5.6 fixes the issue. I am using /usr/share/qemu/ovmf-ia32-code.bin /usr/share/qemu/ovmf-ia32-vars.bin from qemu-ovmf-ia32-202002-1.1.noarch rpm. > Signed-off-by: Ard Biesheuvel > --- > arch/x86/platform/efi/efi_64.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c > index c13fa2150976..6ec58ff60b56 100644 > --- a/arch/x86/platform/efi/efi_64.c > +++ b/arch/x86/platform/efi/efi_64.c > @@ -391,11 +391,11 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages) > > efi_scratch.phys_stack = page_to_phys(page + 1); /* stack grows down */ > > - npages = (_etext - _text) >> PAGE_SHIFT; > + npages = (__end_rodata_aligned - _text) >> PAGE_SHIFT; > text = __pa(_text); > pfn = text >> PAGE_SHIFT; > > - pf = _PAGE_RW | _PAGE_ENC; > + pf = _PAGE_ENC; > if (kernel_map_pages_in_pgd(pgd, pfn, text, npages, pf)) { > pr_err("Failed to map kernel text 1:1\n"); > return 1; > thanks, -- js suse labs