From: Nadav Amit <nadav.amit@gmail.com> To: Andy Lutomirski <luto@amacapital.net> Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>, Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@redhat.com>, LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>, Borislav Petkov <bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>, Peter Zijlstra <peterz@infradead.org>, Damian Tometzki <linux_dti@icloud.com>, linux-integrity <linux-integrity@vger.kernel.org>, LSM List <linux-security-module@vger.kernel.org>, Andrew Morton <akpm@linux-foundation.org>, Kernel Hardening <kernel-hardening@lists.openwall.com>, Linux-MM <linux-mm@kvack.org>, Will Deacon <will.deacon@arm.com>, Ard Biesheuvel <ard.biesheuvel@linaro.org>, Kristen Carlson Accardi <kristen@linux.intel.com>, "Dock, Deneen T" <deneen.t.dock@intel.com>, Kees Cook <keescook@chromium.org>, Dave Hansen <dave.hansen@intel.com> Subject: Re: [PATCH v2 05/20] x86/alternative: initializing temporary mm for patching Date: Mon, 11 Feb 2019 10:04:59 -0800 [thread overview] Message-ID: <6FE10C97-25FF-4E99-A96A-465CBACA935B@gmail.com> (raw) In-Reply-To: <00649AE8-69C0-4CD2-A916-B8C8F0F5DAC3@amacapital.net> > On Feb 10, 2019, at 9:18 PM, Andy Lutomirski <luto@amacapital.net> wrote: > > > > On Feb 10, 2019, at 4:39 PM, Nadav Amit <nadav.amit@gmail.com> wrote: > >>> On Jan 28, 2019, at 4:34 PM, Rick Edgecombe <rick.p.edgecombe@intel.com> wrote: >>> >>> From: Nadav Amit <namit@vmware.com> >>> >>> To prevent improper use of the PTEs that are used for text patching, we >>> want to use a temporary mm struct. We initailize it by copying the init >>> mm. >>> >>> The address that will be used for patching is taken from the lower area >>> that is usually used for the task memory. Doing so prevents the need to >>> frequently synchronize the temporary-mm (e.g., when BPF programs are >>> installed), since different PGDs are used for the task memory. >>> >>> Finally, we randomize the address of the PTEs to harden against exploits >>> that use these PTEs. >>> >>> Cc: Kees Cook <keescook@chromium.org> >>> Cc: Dave Hansen <dave.hansen@intel.com> >>> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> >>> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org> >>> Tested-by: Masami Hiramatsu <mhiramat@kernel.org> >>> Suggested-by: Andy Lutomirski <luto@kernel.org> >>> Signed-off-by: Nadav Amit <namit@vmware.com> >>> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> >>> --- >>> arch/x86/include/asm/pgtable.h | 3 +++ >>> arch/x86/include/asm/text-patching.h | 2 ++ >>> arch/x86/kernel/alternative.c | 3 +++ >>> arch/x86/mm/init_64.c | 36 ++++++++++++++++++++++++++++ >>> init/main.c | 3 +++ >>> 5 files changed, 47 insertions(+) >>> >>> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h >>> index 40616e805292..e8f630d9a2ed 100644 >>> --- a/arch/x86/include/asm/pgtable.h >>> +++ b/arch/x86/include/asm/pgtable.h >>> @@ -1021,6 +1021,9 @@ static inline void __meminit init_trampoline_default(void) >>> /* Default trampoline pgd value */ >>> trampoline_pgd_entry = init_top_pgt[pgd_index(__PAGE_OFFSET)]; >>> } >>> + >>> +void __init poking_init(void); >>> + >>> # ifdef CONFIG_RANDOMIZE_MEMORY >>> void __meminit init_trampoline(void); >>> # else >>> diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h >>> index f8fc8e86cf01..a75eed841eed 100644 >>> --- a/arch/x86/include/asm/text-patching.h >>> +++ b/arch/x86/include/asm/text-patching.h >>> @@ -39,5 +39,7 @@ extern void *text_poke_kgdb(void *addr, const void *opcode, size_t len); >>> extern int poke_int3_handler(struct pt_regs *regs); >>> extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler); >>> extern int after_bootmem; >>> +extern __ro_after_init struct mm_struct *poking_mm; >>> +extern __ro_after_init unsigned long poking_addr; >>> >>> #endif /* _ASM_X86_TEXT_PATCHING_H */ >>> diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c >>> index 12fddbc8c55b..ae05fbb50171 100644 >>> --- a/arch/x86/kernel/alternative.c >>> +++ b/arch/x86/kernel/alternative.c >>> @@ -678,6 +678,9 @@ void *__init_or_module text_poke_early(void *addr, const void *opcode, >>> return addr; >>> } >>> >>> +__ro_after_init struct mm_struct *poking_mm; >>> +__ro_after_init unsigned long poking_addr; >>> + >>> static void *__text_poke(void *addr, const void *opcode, size_t len) >>> { >>> unsigned long flags; >>> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c >>> index bccff68e3267..125c8c48aa24 100644 >>> --- a/arch/x86/mm/init_64.c >>> +++ b/arch/x86/mm/init_64.c >>> @@ -53,6 +53,7 @@ >>> #include <asm/init.h> >>> #include <asm/uv/uv.h> >>> #include <asm/setup.h> >>> +#include <asm/text-patching.h> >>> >>> #include "mm_internal.h" >>> >>> @@ -1383,6 +1384,41 @@ unsigned long memory_block_size_bytes(void) >>> return memory_block_size_probed; >>> } >>> >>> +/* >>> + * Initialize an mm_struct to be used during poking and a pointer to be used >>> + * during patching. >>> + */ >>> +void __init poking_init(void) >>> +{ >>> + spinlock_t *ptl; >>> + pte_t *ptep; >>> + >>> + poking_mm = copy_init_mm(); >>> + BUG_ON(!poking_mm); >>> + >>> + /* >>> + * Randomize the poking address, but make sure that the following page >>> + * will be mapped at the same PMD. We need 2 pages, so find space for 3, >>> + * and adjust the address if the PMD ends after the first one. >>> + */ >>> + poking_addr = TASK_UNMAPPED_BASE; >>> + if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) >>> + poking_addr += (kaslr_get_random_long("Poking") & PAGE_MASK) % >>> + (TASK_SIZE - TASK_UNMAPPED_BASE - 3 * PAGE_SIZE); >>> + >>> + if (((poking_addr + PAGE_SIZE) & ~PMD_MASK) == 0) >>> + poking_addr += PAGE_SIZE; >> >> Further thinking about it, I think that allocating the virtual address for >> poking from user address-range is problematic. The user can set watchpoints >> on different addresses, cause some static-keys to be enabled/disabled, and >> monitor the signals to derandomize the poking address. > > Hmm, I hadn’t thought about watchpoints. I’m not sure how much we care > about possible derandomization like this, but we certainly don’t want to > send signals or otherwise malfunction. > >> Andy, I think you were pushing this change. Can I go back to use a vmalloc’d >> address instead, or do you have a better solution? > > Hmm. If we use a vmalloc address, we have to make sure it’s not actually > allocated. I suppose we could allocate one once at boot and use that. We > also have the problem that the usual APIs for handling “user” addresses > might assume they’re actually in the user range, although this seems > unlikely to be a problem in practice. More seriously, though, the code > that manipulates per-mm paging structures assumes that *all* of the > structures up to the top level are per-mm, and, if we use anything less > than a private pgd, this isn’t the case. I forgot that I only had this conversation in my mind ;-) Well, I did write some code that kept some vmalloc’d area private, and it did require more synchronization between the pgd’s. It is still possible to use another top-level PGD, but … (continued below) > >> I prefer not to >> save/restore DR7, of course. > > I suspect we may want to use the temporary mm concept for EFI, too, so we > may want to just suck it up and save/restore DR7. But only if a watchpoint > is in use, of course. I have an old patch I could dust off that tracks DR7 > to make things like this efficient. … but, if this is the case, then I will just make (un)use_temporary_mm() to save/restore DR7. I guess you are ok with such a solution. I will incorporate it into Rick’s v3.
next prev parent reply other threads:[~2019-02-11 18:05 UTC|newest] Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-01-29 0:34 [PATCH v2 00/20] Merge text_poke fixes and executable lockdowns Rick Edgecombe 2019-01-29 0:34 ` [PATCH v2 01/20] Fix "x86/alternatives: Lockdep-enforce text_mutex in text_poke*()" Rick Edgecombe 2019-01-29 0:34 ` [PATCH v2 02/20] x86/jump_label: Use text_poke_early() during early init Rick Edgecombe 2019-01-29 0:34 ` [PATCH v2 03/20] x86/mm: temporary mm struct Rick Edgecombe 2019-01-31 11:29 ` Borislav Petkov 2019-01-31 22:19 ` Nadav Amit 2019-02-01 0:08 ` Borislav Petkov 2019-02-01 0:25 ` Nadav Amit 2019-02-04 14:28 ` Borislav Petkov 2019-01-29 0:34 ` [PATCH v2 04/20] fork: provide a function for copying init_mm Rick Edgecombe 2019-02-05 8:53 ` Borislav Petkov 2019-02-05 9:03 ` Nadav Amit 2019-01-29 0:34 ` [PATCH v2 05/20] x86/alternative: initializing temporary mm for patching Rick Edgecombe 2019-02-05 9:18 ` Borislav Petkov 2019-02-11 0:39 ` Nadav Amit 2019-02-11 5:18 ` Andy Lutomirski 2019-02-11 18:04 ` Nadav Amit [this message] 2019-02-11 19:07 ` Andy Lutomirski 2019-02-11 19:18 ` Nadav Amit 2019-02-11 22:47 ` Andy Lutomirski 2019-02-12 18:23 ` Nadav Amit 2019-01-29 0:34 ` [PATCH v2 06/20] x86/alternative: use temporary mm for text poking Rick Edgecombe 2019-02-05 9:58 ` Borislav Petkov 2019-02-05 11:31 ` Peter Zijlstra 2019-02-05 12:35 ` Borislav Petkov 2019-02-05 13:25 ` Peter Zijlstra 2019-02-05 17:54 ` Nadav Amit 2019-02-05 13:29 ` Peter Zijlstra 2019-01-29 0:34 ` [PATCH v2 07/20] x86/kgdb: avoid redundant comparison of patched code Rick Edgecombe 2019-01-29 0:34 ` [PATCH v2 08/20] x86/ftrace: set trampoline pages as executable Rick Edgecombe 2019-01-29 0:34 ` [PATCH v2 09/20] x86/kprobes: instruction pages initialization enhancements Rick Edgecombe 2019-02-11 18:22 ` Borislav Petkov 2019-02-11 19:36 ` Nadav Amit 2019-01-29 0:34 ` [PATCH v2 10/20] x86: avoid W^X being broken during modules loading Rick Edgecombe 2019-02-11 18:29 ` Borislav Petkov 2019-02-11 18:45 ` Nadav Amit 2019-02-11 19:01 ` Borislav Petkov 2019-02-11 19:09 ` Nadav Amit 2019-02-11 19:10 ` Borislav Petkov 2019-02-11 19:27 ` Nadav Amit 2019-02-11 19:42 ` Borislav Petkov 2019-02-11 20:32 ` Nadav Amit 2019-03-07 15:10 ` [PATCH] x86/cpufeature: Remove __pure attribute to _static_cpu_has() Borislav Petkov 2019-03-07 16:43 ` hpa 2019-03-07 17:02 ` Borislav Petkov 2019-03-07 7:29 ` [PATCH v2 10/20] x86: avoid W^X being broken during modules loading Borislav Petkov 2019-03-07 16:53 ` hpa 2019-03-07 17:06 ` Borislav Petkov 2019-03-07 20:02 ` Andy Lutomirski 2019-03-07 20:25 ` Borislav Petkov 2019-01-29 0:34 ` [PATCH v2 11/20] x86/jump-label: remove support for custom poker Rick Edgecombe 2019-02-11 18:37 ` Borislav Petkov 2019-01-29 0:34 ` [PATCH v2 12/20] x86/alternative: Remove the return value of text_poke_*() Rick Edgecombe 2019-01-29 0:34 ` [PATCH v2 13/20] Add set_alias_ function and x86 implementation Rick Edgecombe 2019-02-11 19:09 ` Borislav Petkov 2019-02-11 19:27 ` Edgecombe, Rick P 2019-02-11 22:59 ` Andy Lutomirski 2019-02-12 0:01 ` Edgecombe, Rick P 2019-01-29 0:34 ` [PATCH v2 14/20] mm: Make hibernate handle unmapped pages Rick Edgecombe 2019-02-19 11:04 ` Borislav Petkov 2019-02-19 21:28 ` Edgecombe, Rick P 2019-02-20 16:07 ` Borislav Petkov 2019-01-29 0:34 ` [PATCH v2 15/20] vmalloc: New flags for safe vfree on special perms Rick Edgecombe 2019-02-19 12:48 ` Borislav Petkov 2019-02-19 19:42 ` Edgecombe, Rick P 2019-02-20 16:14 ` Borislav Petkov 2019-01-29 0:34 ` [PATCH v2 16/20] modules: Use vmalloc special flag Rick Edgecombe 2019-01-29 0:34 ` [PATCH v2 17/20] bpf: " Rick Edgecombe 2019-01-29 0:34 ` [PATCH v2 18/20] x86/ftrace: " Rick Edgecombe 2019-01-29 0:34 ` [PATCH v2 19/20] x86/kprobes: " Rick Edgecombe 2019-01-29 0:34 ` [PATCH v2 20/20] x86/alternative: comment about module removal races Rick Edgecombe
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=6FE10C97-25FF-4E99-A96A-465CBACA935B@gmail.com \ --to=nadav.amit@gmail.com \ --cc=akpm@linux-foundation.org \ --cc=ard.biesheuvel@linaro.org \ --cc=bp@alien8.de \ --cc=dave.hansen@intel.com \ --cc=dave.hansen@linux.intel.com \ --cc=deneen.t.dock@intel.com \ --cc=hpa@zytor.com \ --cc=keescook@chromium.org \ --cc=kernel-hardening@lists.openwall.com \ --cc=kristen@linux.intel.com \ --cc=linux-integrity@vger.kernel.org \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-mm@kvack.org \ --cc=linux-security-module@vger.kernel.org \ --cc=linux_dti@icloud.com \ --cc=luto@amacapital.net \ --cc=luto@kernel.org \ --cc=mingo@redhat.com \ --cc=peterz@infradead.org \ --cc=rick.p.edgecombe@intel.com \ --cc=tglx@linutronix.de \ --cc=will.deacon@arm.com \ --cc=x86@kernel.org \ --subject='Re: [PATCH v2 05/20] x86/alternative: initializing temporary mm for patching' \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: link
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).