From: Andy Lutomirski <luto@kernel.org>
To: Yu-cheng Yu <yu-cheng.yu@intel.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
linux-doc@vger.kernel.org, Linux-MM <linux-mm@kvack.org>,
linux-arch <linux-arch@vger.kernel.org>, X86 ML <x86@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. J. Lu" <hjl.tools@gmail.com>,
"Shanbhogue, Vedvyas" <vedvyas.shanbhogue@intel.com>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Jonathan Corbet <corbet@lwn.net>, Oleg Nesterov <oleg@redhat.com>,
Arnd Bergmann <arnd@arndb.de>,
mike.kravetz@oracle.com
Subject: Re: [PATCH 05/10] x86/cet: ELF header parsing of Control Flow Enforcement
Date: Thu, 7 Jun 2018 11:38:02 -0700 [thread overview]
Message-ID: <CALCETrVyGdWnU1B5vZK4QP2TGVjTCg5wsPX8iAQRGzpcGNGr5g@mail.gmail.com> (raw)
In-Reply-To: <20180607143807.3611-6-yu-cheng.yu@intel.com>
On Thu, Jun 7, 2018 at 7:41 AM Yu-cheng Yu <yu-cheng.yu@intel.com> wrote:
>
> Look in .note.gnu.property of an ELF file and check if shadow stack needs
> to be enabled for the task.
Nice! But please structure it so it's one function that parses out
all the ELF notes and some other code (a table or a switch statement)
that handles them. We will probably want to add more kernel-parsed
ELF notes some day, so let's structure the code to make it easier.
> +static int find_cet(u8 *buf, u32 size, u32 align, int *shstk, int *ibt)
> +{
> + unsigned long start = (unsigned long)buf;
> + struct elf_note *note = (struct elf_note *)buf;
> +
> + *shstk = 0;
> + *ibt = 0;
> +
> + /*
> + * Go through the x86_note_gnu_property array pointed by
> + * buf and look for shadow stack and indirect branch
> + * tracking features.
> + * The GNU_PROPERTY_X86_FEATURE_1_AND entry contains only
> + * one u32 as data. Do not go beyond buf_size.
> + */
> +
> + while ((unsigned long) (note + 1) - start < size) {
> + /* Find the NT_GNU_PROPERTY_TYPE_0 note. */
> + if (note->n_namesz == 4 &&
> + note->n_type == NT_GNU_PROPERTY_TYPE_0 &&
> + memcmp(note + 1, "GNU", 4) == 0) {
> + u8 *ptr, *ptr_end;
> +
> + /* Check for invalid property. */
> + if (note->n_descsz < 8 ||
> + (note->n_descsz % align) != 0)
> + return 0;
> +
> + /* Start and end of property array. */
> + ptr = (u8 *)(note + 1) + 4;
> + ptr_end = ptr + note->n_descsz;
Exploitable bug here? You haven't checked that ptr is in bounds or
that ptr + ptr_end is in bounds (or that ptr_end > ptr, for that
matter).
> +
> + while (1) {
> + u32 type = *(u32 *)ptr;
> + u32 datasz = *(u32 *)(ptr + 4);
> +
> + ptr += 8;
> + if ((ptr + datasz) > ptr_end)
> + break;
> +
> + if (type == GNU_PROPERTY_X86_FEATURE_1_AND &&
> + datasz == 4) {
> + u32 p = *(u32 *)ptr;
> +
> + if (p & GNU_PROPERTY_X86_FEATURE_1_SHSTK)
> + *shstk = 1;
> + if (p & GNU_PROPERTY_X86_FEATURE_1_IBT)
> + *ibt = 1;
> + return 1;
> + }
> + }
> + }
> +
> + /*
> + * Note sections like .note.ABI-tag and .note.gnu.build-id
> + * are aligned to 4 bytes in 64-bit ELF objects.
> + */
> + note = (void *)note + ELF_NOTE_NEXT_OFFSET(note, align);
A malicious value here will probably just break out of the while
statement, but it's still scary.
> + }
> +
> + return 0;
> +}
> +
> +static int check_pt_note_segment(struct file *file,
> + unsigned long note_size, loff_t *pos,
> + u32 align, int *shstk, int *ibt)
> +{
> + int retval;
> + char *note_buf;
> +
> + /*
> + * Try to read in the whole PT_NOTE segment.
> + */
> + note_buf = kmalloc(note_size, GFP_KERNEL);
kmalloc() with fully user-controlled, unchecked size is not a good idea.
next prev parent reply other threads:[~2018-06-07 18:38 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-07 14:37 [PATCH 00/10] Control Flow Enforcement - Part (3) Yu-cheng Yu
2018-06-07 14:37 ` [PATCH 01/10] x86/cet: User-mode shadow stack support Yu-cheng Yu
2018-06-07 16:37 ` Andy Lutomirski
2018-06-07 17:46 ` Yu-cheng Yu
2018-06-07 17:55 ` Dave Hansen
2018-06-07 18:23 ` Andy Lutomirski
2018-06-12 11:56 ` Balbir Singh
2018-06-12 15:03 ` Yu-cheng Yu
2018-06-07 14:37 ` [PATCH 02/10] x86/cet: Introduce WRUSS instruction Yu-cheng Yu
2018-06-07 16:40 ` Andy Lutomirski
2018-06-07 16:51 ` Yu-cheng Yu
2018-06-07 18:41 ` Peter Zijlstra
2018-06-07 20:31 ` Yu-cheng Yu
2018-06-11 8:17 ` Peter Zijlstra
2018-06-11 15:02 ` Yu-cheng Yu
2018-06-14 1:30 ` Balbir Singh
2018-06-14 14:43 ` Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 03/10] x86/cet: Signal handling for shadow stack Yu-cheng Yu
2018-06-07 18:30 ` Andy Lutomirski
2018-06-07 18:58 ` Florian Weimer
2018-06-07 19:51 ` Yu-cheng Yu
2018-06-07 20:07 ` Cyrill Gorcunov
2018-06-07 20:57 ` Andy Lutomirski
2018-06-08 12:07 ` Cyrill Gorcunov
2018-06-07 20:12 ` Yu-cheng Yu
2018-06-07 20:17 ` Dave Hansen
2018-06-07 14:38 ` [PATCH 04/10] x86/cet: Handle thread " Yu-cheng Yu
2018-06-07 18:21 ` Andy Lutomirski
2018-06-07 19:47 ` Florian Weimer
2018-06-07 20:53 ` Andy Lutomirski
2018-06-08 14:53 ` Florian Weimer
2018-06-08 15:01 ` Andy Lutomirski
2018-06-08 15:50 ` Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 05/10] x86/cet: ELF header parsing of Control Flow Enforcement Yu-cheng Yu
2018-06-07 18:38 ` Andy Lutomirski [this message]
2018-06-07 20:40 ` Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 06/10] x86/cet: Add arch_prctl functions for shadow stack Yu-cheng Yu
2018-06-07 18:48 ` Andy Lutomirski
2018-06-07 20:30 ` Yu-cheng Yu
2018-06-07 21:01 ` Andy Lutomirski
2018-06-07 22:02 ` H.J. Lu
2018-06-07 23:01 ` Andy Lutomirski
2018-06-08 4:09 ` H.J. Lu
2018-06-08 4:38 ` Andy Lutomirski
2018-06-08 12:24 ` H.J. Lu
2018-06-08 14:57 ` Andy Lutomirski
2018-06-08 15:52 ` Cyrill Gorcunov
2018-06-08 4:22 ` H.J. Lu
2018-06-08 4:35 ` Andy Lutomirski
2018-06-08 12:17 ` H.J. Lu
2018-06-12 10:03 ` Thomas Gleixner
2018-06-12 11:43 ` H.J. Lu
2018-06-12 16:01 ` Andy Lutomirski
2018-06-12 16:05 ` H.J. Lu
2018-06-12 16:34 ` Andy Lutomirski
2018-06-12 16:51 ` H.J. Lu
2018-06-12 18:59 ` Thomas Gleixner
2018-06-12 19:34 ` H.J. Lu
2018-06-18 22:03 ` Andy Lutomirski
2018-06-19 0:52 ` Kees Cook
2018-06-19 6:40 ` Florian Weimer
2018-06-19 14:50 ` Andy Lutomirski
2018-06-19 16:44 ` Kees Cook
2018-06-19 16:59 ` Yu-cheng Yu
2018-06-19 17:07 ` Kees Cook
2018-06-19 17:20 ` Andy Lutomirski
2018-06-19 20:12 ` Kees Cook
2018-06-19 20:47 ` Andy Lutomirski
2018-06-19 22:38 ` Yu-cheng Yu
2018-06-20 0:50 ` Andy Lutomirski
2018-06-21 23:07 ` Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 07/10] mm: Prevent mprotect from changing " Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 08/10] mm: Prevent mremap of " Yu-cheng Yu
2018-06-07 18:48 ` Andy Lutomirski
2018-06-07 20:18 ` Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 09/10] mm: Prevent madvise from changing " Yu-cheng Yu
2018-06-07 20:54 ` Andy Lutomirski
2018-06-07 21:09 ` Nadav Amit
2018-06-07 21:18 ` Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 10/10] mm: Prevent munmap and remap_file_pages of " Yu-cheng Yu
2018-06-07 18:50 ` Andy Lutomirski
2018-06-07 20:15 ` Yu-cheng Yu
2018-06-12 10:56 ` [PATCH 00/10] Control Flow Enforcement - Part (3) Balbir Singh
2018-06-12 15:03 ` Yu-cheng Yu
2018-06-12 16:00 ` Andy Lutomirski
2018-06-12 16:21 ` Yu-cheng Yu
2018-06-12 16:31 ` Andy Lutomirski
2018-06-12 17:24 ` Yu-cheng Yu
2018-06-12 20:15 ` Yu-cheng Yu
2018-06-14 1:07 ` Balbir Singh
2018-06-14 14:56 ` Yu-cheng Yu
2018-06-17 3:16 ` Balbir Singh
2018-06-18 21:44 ` Andy Lutomirski
2018-06-19 8:52 ` Balbir Singh
2018-06-26 2:46 ` Jann Horn
2018-06-26 14:56 ` Yu-cheng Yu
2018-06-26 5:26 ` Andy Lutomirski
2018-06-26 14:56 ` Yu-cheng Yu
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