From: "H.J. Lu" <hjl.tools@gmail.com>
To: John Allen <john.allen@amd.com>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>,
"the arch/x86 maintainers" <x86@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
linux-arch <linux-arch@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>,
Arnd Bergmann <arnd@arndb.de>, Andy Lutomirski <luto@kernel.org>,
Balbir Singh <bsingharora@gmail.com>,
Borislav Petkov <bp@alien8.de>,
Cyrill Gorcunov <gorcunov@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Eugene Syromiatnikov <esyr@redhat.com>,
Florian Weimer <fweimer@redhat.com>,
Jann Horn <jannh@google.com>, Jonathan Corbet <corbet@lwn.net>,
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Nadav Amit <nadav.amit@gmail.com>,
Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
Peter Zijlstra <peterz@infradead.org>,
Randy Dunlap <rdunlap@infradead.org>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
Dave Martin <Dave.Martin@arm.com>,
Weijiang Yang <weijiang.yang@intel.com>,
Pengfei Xu <pengfei.xu@intel.com>,
Haitao Huang <haitao.huang@intel.com>
Subject: Re: [PATCH v27 24/31] x86/cet/shstk: Handle thread shadow stack
Date: Wed, 21 Jul 2021 13:14:37 -0700 [thread overview]
Message-ID: <CAMe9rOqwe8Mr2pkf0yopWj_F7yZLj9_nmz97+AmFkkmd2U=-fg@mail.gmail.com> (raw)
In-Reply-To: <YPhkIHJ0guc4UNoO@AUS-LX-JohALLEN.amd.com>
On Wed, Jul 21, 2021 at 11:15 AM John Allen <john.allen@amd.com> wrote:
>
> On Fri, May 21, 2021 at 03:12:04PM -0700, Yu-cheng Yu wrote:
> > diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c
> > index 5ea2b494e9f9..8e5f772181b9 100644
> > --- a/arch/x86/kernel/shstk.c
> > +++ b/arch/x86/kernel/shstk.c
> > @@ -71,6 +71,53 @@ int shstk_setup(void)
> > return 0;
> > }
> >
> > +int shstk_alloc_thread_stack(struct task_struct *tsk, unsigned long clone_flags,
> > + unsigned long stack_size)
> > +{
> > + struct thread_shstk *shstk = &tsk->thread.shstk;
> > + struct cet_user_state *state;
> > + unsigned long addr;
> > +
> > + if (!stack_size)
> > + return -EINVAL;
>
> I've been doing some light testing on AMD hardware and I've found that
> this version of the patchset doesn't boot for me. It appears that when
> systemd processes start spawning, they hit the above case, return
> -EINVAL, and the fork fails. In these cases, copy_thread has been passed
> 0 for both sp and stack_size.
>
> For previous versions of the patchset, I can still boot. When the
> stack_size check was last, the function would always return before
> completing the check, hitting one of the two cases below.
>
> At the very least, it would seem that on some systems, it isn't valid to
> rely on the stack_size passed from clone3, though I'm unsure what the
> correct behavior should be here. If the passed stack_size == 0 and sp ==
> 0, is this a case where we want to alloc a shadow stack for this thread
> with some capped size? Alternatively, is this a case that isn't valid to
> alloc a shadow stack and we should simply return 0 instead of -EINVAL?
>
> I'm running Fedora 34 which satisfies the required versions of gcc,
> binutils, and glibc.
>
> Please let me know if there is any additional information I can provide.
FWIW, I have been maintaining stable CET kernels at:
https://github.com/hjl-tools/linux/
The current CET kernel is on hjl/cet/linux-5.13.y branch.
> Thanks,
> John
>
> > +
> > + if (!shstk->size)
> > + return 0;
> > +
> > + /*
> > + * For CLONE_VM, except vfork, the child needs a separate shadow
> > + * stack.
> > + */
> > + if ((clone_flags & (CLONE_VFORK | CLONE_VM)) != CLONE_VM)
> > + return 0;
> > +
> > + state = get_xsave_addr(&tsk->thread.fpu.state.xsave, XFEATURE_CET_USER);
> > + if (!state)
> > + return -EINVAL;
> > +
> > + /*
> > + * Compat-mode pthreads share a limited address space.
> > + * If each function call takes an average of four slots
> > + * stack space, allocate 1/4 of stack size for shadow stack.
> > + */
> > + if (in_compat_syscall())
> > + stack_size /= 4;
> > +
> > + stack_size = round_up(stack_size, PAGE_SIZE);
> > + addr = alloc_shstk(stack_size);
> > + if (IS_ERR_VALUE(addr)) {
> > + shstk->base = 0;
> > + shstk->size = 0;
> > + return PTR_ERR((void *)addr);
> > + }
> > +
> > + fpu__prepare_write(&tsk->thread.fpu);
> > + state->user_ssp = (u64)(addr + stack_size);
> > + shstk->base = addr;
> > + shstk->size = stack_size;
> > + return 0;
> > +}
> > +
> > void shstk_free(struct task_struct *tsk)
> > {
> > struct thread_shstk *shstk = &tsk->thread.shstk;
> > @@ -80,7 +127,13 @@ void shstk_free(struct task_struct *tsk)
> > !shstk->base)
> > return;
> >
> > - if (!tsk->mm)
> > + /*
> > + * When fork() with CLONE_VM fails, the child (tsk) already has a
> > + * shadow stack allocated, and exit_thread() calls this function to
> > + * free it. In this case the parent (current) and the child share
> > + * the same mm struct.
> > + */
> > + if (!tsk->mm || tsk->mm != current->mm)
> > return;
> >
> > while (1) {
--
H.J.
next prev parent reply other threads:[~2021-07-21 20:15 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-21 22:11 [PATCH v27 00/31] Control-flow Enforcement: Shadow Stack Yu-cheng Yu
2021-05-21 22:11 ` [PATCH v27 01/31] Documentation/x86: Add CET description Yu-cheng Yu
2021-05-21 22:11 ` [PATCH v27 02/31] x86/cet/shstk: Add Kconfig option for Shadow Stack Yu-cheng Yu
2021-05-21 22:11 ` [PATCH v27 03/31] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (CET) Yu-cheng Yu
2021-05-21 22:11 ` [PATCH v27 04/31] x86/cpufeatures: Introduce CPU setup and option parsing for CET Yu-cheng Yu
2021-05-21 22:11 ` [PATCH v27 05/31] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states Yu-cheng Yu
2021-05-21 22:11 ` [PATCH v27 06/31] x86/cet: Add control-protection fault handler Yu-cheng Yu
2021-05-21 22:11 ` [PATCH v27 07/31] x86/mm: Remove _PAGE_DIRTY from kernel RO pages Yu-cheng Yu
2021-05-21 22:11 ` [PATCH v27 08/31] x86/mm: Move pmd_write(), pud_write() up in the file Yu-cheng Yu
2021-05-21 22:11 ` [PATCH v27 09/31] x86/mm: Introduce _PAGE_COW Yu-cheng Yu
2021-05-21 22:11 ` [PATCH v27 10/31] drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS Yu-cheng Yu
2021-05-21 22:11 ` [PATCH v27 11/31] x86/mm: Update pte_modify for _PAGE_COW Yu-cheng Yu
2021-05-21 22:11 ` [PATCH v27 12/31] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY to _PAGE_COW Yu-cheng Yu
2021-05-21 22:11 ` [PATCH v27 13/31] mm: Move VM_UFFD_MINOR_BIT from 37 to 38 Yu-cheng Yu
2021-05-21 22:25 ` Axel Rasmussen
2021-05-22 1:58 ` Yu, Yu-cheng
2021-05-21 22:11 ` [PATCH v27 14/31] mm: Introduce VM_SHADOW_STACK for shadow stack memory Yu-cheng Yu
2021-05-21 22:11 ` [PATCH v27 15/31] x86/mm: Shadow Stack page fault error checking Yu-cheng Yu
2021-05-21 22:11 ` [PATCH v27 16/31] x86/mm: Update maybe_mkwrite() for shadow stack Yu-cheng Yu
2021-05-21 22:11 ` [PATCH v27 17/31] mm: Fixup places that call pte_mkwrite() directly Yu-cheng Yu
2021-05-21 22:11 ` [PATCH v27 18/31] mm: Add guard pages around a shadow stack Yu-cheng Yu
2021-05-21 22:11 ` [PATCH v27 19/31] mm/mmap: Add shadow stack pages to memory accounting Yu-cheng Yu
2021-05-21 22:12 ` [PATCH v27 20/31] mm: Update can_follow_write_pte() for shadow stack Yu-cheng Yu
2021-05-21 22:12 ` [PATCH v27 21/31] mm/mprotect: Exclude shadow stack from preserve_write Yu-cheng Yu
2021-05-21 22:12 ` [PATCH v27 22/31] mm: Re-introduce vm_flags to do_mmap() Yu-cheng Yu
2021-05-21 22:12 ` [PATCH v27 23/31] x86/cet/shstk: Add user-mode shadow stack support Yu-cheng Yu
2021-07-19 18:23 ` Edgecombe, Rick P
2021-07-20 17:13 ` Yu, Yu-cheng
2021-05-21 22:12 ` [PATCH v27 24/31] x86/cet/shstk: Handle thread shadow stack Yu-cheng Yu
2021-05-22 23:39 ` Andy Lutomirski
2021-05-25 15:04 ` Yu, Yu-cheng
2021-07-21 18:14 ` John Allen
2021-07-21 18:28 ` Florian Weimer
2021-07-21 18:34 ` Yu, Yu-cheng
2021-07-28 21:34 ` John Allen
2021-07-21 18:37 ` Dave Hansen
2021-07-21 20:14 ` H.J. Lu [this message]
2021-05-21 22:12 ` [PATCH v27 25/31] x86/cet/shstk: Introduce shadow stack token setup/verify routines Yu-cheng Yu
2021-05-21 22:12 ` [PATCH v27 26/31] x86/cet/shstk: Handle signals for shadow stack Yu-cheng Yu
2021-05-21 22:12 ` [PATCH v27 27/31] ELF: Introduce arch_setup_elf_property() Yu-cheng Yu
2021-05-25 10:54 ` Catalin Marinas
2021-05-21 22:12 ` [PATCH v27 28/31] x86/cet/shstk: Add arch_prctl functions for shadow stack Yu-cheng Yu
2021-05-21 22:12 ` [PATCH v27 29/31] mm: Move arch_calc_vm_prot_bits() to arch/x86/include/asm/mman.h Yu-cheng Yu
2021-05-21 22:12 ` [PATCH v27 30/31] mm: Update arch_validate_flags() to test vma anonymous Yu-cheng Yu
2021-05-25 11:00 ` Catalin Marinas
2021-05-25 15:03 ` Yu, Yu-cheng
2021-05-21 22:12 ` [PATCH v27 31/31] mm: Introduce PROT_SHADOW_STACK for shadow stack Yu-cheng Yu
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