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  1. 29 8月, 2017 5 次提交
  3. 25 8月, 2017 4 次提交
    • E
      x86/mm: Fix use-after-free of ldt_struct · ccd5b323
      由 Eric Biggers 提交于 
      The following commit:

  39a0526f ("x86/mm: Factor out LDT init from context init")

renamed init_new_context() to init_new_context_ldt() and added a new
init_new_context() which calls init_new_context_ldt().  However, the
error code of init_new_context_ldt() was ignored.  Consequently, if a
memory allocation in alloc_ldt_struct() failed during a fork(), the
->context.ldt of the new task remained the same as that of the old task
(due to the memcpy() in dup_mm()).  ldt_struct's are not intended to be
shared, so a use-after-free occurred after one task exited.

Fix the bug by making init_new_context() pass through the error code of
init_new_context_ldt().

This bug was found by syzkaller, which encountered the following splat:

    BUG: KASAN: use-after-free in free_ldt_struct.part.2+0x10a/0x150 arch/x86/kernel/ldt.c:116
    Read of size 4 at addr ffff88006d2cb7c8 by task kworker/u9:0/3710

    CPU: 1 PID: 3710 Comm: kworker/u9:0 Not tainted 4.13.0-rc4-next-20170811 #2
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
    Call Trace:
     __dump_stack lib/dump_stack.c:16 [inline]
     dump_stack+0x194/0x257 lib/dump_stack.c:52
     print_address_description+0x73/0x250 mm/kasan/report.c:252
     kasan_report_error mm/kasan/report.c:351 [inline]
     kasan_report+0x24e/0x340 mm/kasan/report.c:409
     __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:429
     free_ldt_struct.part.2+0x10a/0x150 arch/x86/kernel/ldt.c:116
     free_ldt_struct arch/x86/kernel/ldt.c:173 [inline]
     destroy_context_ldt+0x60/0x80 arch/x86/kernel/ldt.c:171
     destroy_context arch/x86/include/asm/mmu_context.h:157 [inline]
     __mmdrop+0xe9/0x530 kernel/fork.c:889
     mmdrop include/linux/sched/mm.h:42 [inline]
     exec_mmap fs/exec.c:1061 [inline]
     flush_old_exec+0x173c/0x1ff0 fs/exec.c:1291
     load_elf_binary+0x81f/0x4ba0 fs/binfmt_elf.c:855
     search_binary_handler+0x142/0x6b0 fs/exec.c:1652
     exec_binprm fs/exec.c:1694 [inline]
     do_execveat_common.isra.33+0x1746/0x22e0 fs/exec.c:1816
     do_execve+0x31/0x40 fs/exec.c:1860
     call_usermodehelper_exec_async+0x457/0x8f0 kernel/umh.c:100
     ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

    Allocated by task 3700:
     save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
     save_stack+0x43/0xd0 mm/kasan/kasan.c:447
     set_track mm/kasan/kasan.c:459 [inline]
     kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
     kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3627
     kmalloc include/linux/slab.h:493 [inline]
     alloc_ldt_struct+0x52/0x140 arch/x86/kernel/ldt.c:67
     write_ldt+0x7b7/0xab0 arch/x86/kernel/ldt.c:277
     sys_modify_ldt+0x1ef/0x240 arch/x86/kernel/ldt.c:307
     entry_SYSCALL_64_fastpath+0x1f/0xbe

    Freed by task 3700:
     save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
     save_stack+0x43/0xd0 mm/kasan/kasan.c:447
     set_track mm/kasan/kasan.c:459 [inline]
     kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
     __cache_free mm/slab.c:3503 [inline]
     kfree+0xca/0x250 mm/slab.c:3820
     free_ldt_struct.part.2+0xdd/0x150 arch/x86/kernel/ldt.c:121
     free_ldt_struct arch/x86/kernel/ldt.c:173 [inline]
     destroy_context_ldt+0x60/0x80 arch/x86/kernel/ldt.c:171
     destroy_context arch/x86/include/asm/mmu_context.h:157 [inline]
     __mmdrop+0xe9/0x530 kernel/fork.c:889
     mmdrop include/linux/sched/mm.h:42 [inline]
     __mmput kernel/fork.c:916 [inline]
     mmput+0x541/0x6e0 kernel/fork.c:927
     copy_process.part.36+0x22e1/0x4af0 kernel/fork.c:1931
     copy_process kernel/fork.c:1546 [inline]
     _do_fork+0x1ef/0xfb0 kernel/fork.c:2025
     SYSC_clone kernel/fork.c:2135 [inline]
     SyS_clone+0x37/0x50 kernel/fork.c:2129
     do_syscall_64+0x26c/0x8c0 arch/x86/entry/common.c:287
     return_from_SYSCALL_64+0x0/0x7a

Here is a C reproducer:

    #include <asm/ldt.h>
    #include <pthread.h>
    #include <signal.h>
    #include <stdlib.h>
    #include <sys/syscall.h>
    #include <sys/wait.h>
    #include <unistd.h>

    static void *fork_thread(void *_arg)
    {
        fork();
    }

    int main(void)
    {
        struct user_desc desc = { .entry_number = 8191 };

        syscall(__NR_modify_ldt, 1, &desc, sizeof(desc));

        for (;;) {
            if (fork() == 0) {
                pthread_t t;

                srand(getpid());
                pthread_create(&t, NULL, fork_thread, NULL);
                usleep(rand() % 10000);
                syscall(__NR_exit_group, 0);
            }
            wait(NULL);
        }
    }

Note: the reproducer takes advantage of the fact that alloc_ldt_struct()
may use vmalloc() to allocate a large ->entries array, and after
commit:

  5d17a73a ("vmalloc: back off when the current task is killed")

it is possible for userspace to fail a task's vmalloc() by
sending a fatal signal, e.g. via exit_group().  It would be more
difficult to reproduce this bug on kernels without that commit.

This bug only affected kernels with CONFIG_MODIFY_LDT_SYSCALL=y.
Signed-off-by: NEric Biggers <ebiggers@google.com>
Acked-by: NDave Hansen <dave.hansen@linux.intel.com>
Cc: <stable@vger.kernel.org> [v4.6+]
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Fixes: 39a0526f ("x86/mm: Factor out LDT init from context init")
Link: http://lkml.kernel.org/r/20170824175029.76040-1-ebiggers3@gmail.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      ccd5b323
    • P
      KVM, pkeys: do not use PKRU value in vcpu->arch.guest_fpu.state · 38cfd5e3
      由 Paolo Bonzini 提交于 
      The host pkru is restored right after vcpu exit (commit 1be0e61c), so
KVM_GET_XSAVE will return the host PKRU value instead.  Fix this by
using the guest PKRU explicitly in fill_xsave and load_xsave.  This
part is based on a patch by Junkang Fu.

The host PKRU data may also not match the value in vcpu->arch.guest_fpu.state,
because it could have been changed by userspace since the last time
it was saved, so skip loading it in kvm_load_guest_fpu.
Reported-by: NJunkang Fu <junkang.fjk@alibaba-inc.com>
Cc: Yang Zhang <zy107165@alibaba-inc.com>
Fixes: 1be0e61c
Cc: stable@vger.kernel.org
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      38cfd5e3
    • P
      KVM: x86: simplify handling of PKRU · b9dd21e1
      由 Paolo Bonzini 提交于 
      Move it to struct kvm_arch_vcpu, replacing guest_pkru_valid with a
simple comparison against the host value of the register.  The write of
PKRU in addition can be skipped if the guest has not enabled the feature.
Once we do this, we need not test OSPKE in the host anymore, because
guest_CR4.PKE=1 implies host_CR4.PKE=1.

The static PKU test is kept to elide the code on older CPUs.
Suggested-by: NYang Zhang <zy107165@alibaba-inc.com>
Fixes: 1be0e61c
Cc: stable@vger.kernel.org
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      b9dd21e1
    • P
      KVM: x86: block guest protection keys unless the host has them enabled · c469268c
      由 Paolo Bonzini 提交于 
      If the host has protection keys disabled, we cannot read and write the
guest PKRU---RDPKRU and WRPKRU fail with #GP(0) if CR4.PKE=0.  Block
the PKU cpuid bit in that case.

This ensures that guest_CR4.PKE=1 implies host_CR4.PKE=1.

Fixes: 1be0e61c
Cc: stable@vger.kernel.org
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      c469268c
  5. 24 8月, 2017 2 次提交
  7. 23 8月, 2017 1 次提交
  9. 19 8月, 2017 2 次提交
  11. 18 8月, 2017 2 次提交
    • T
      kernel/watchdog: Prevent false positives with turbo modes · 7edaeb68
      由 Thomas Gleixner 提交于 
      The hardlockup detector on x86 uses a performance counter based on unhalted
CPU cycles and a periodic hrtimer. The hrtimer period is about 2/5 of the
performance counter period, so the hrtimer should fire 2-3 times before the
performance counter NMI fires. The NMI code checks whether the hrtimer
fired since the last invocation. If not, it assumess a hard lockup.

The calculation of those periods is based on the nominal CPU
frequency. Turbo modes increase the CPU clock frequency and therefore
shorten the period of the perf/NMI watchdog. With extreme Turbo-modes (3x
nominal frequency) the perf/NMI period is shorter than the hrtimer period
which leads to false positives.

A simple fix would be to shorten the hrtimer period, but that comes with
the side effect of more frequent hrtimer and softlockup thread wakeups,
which is not desired.

Implement a low pass filter, which checks the perf/NMI period against
kernel time. If the perf/NMI fires before 4/5 of the watchdog period has
elapsed then the event is ignored and postponed to the next perf/NMI.

That solves the problem and avoids the overhead of shorter hrtimer periods
and more frequent softlockup thread wakeups.

Fixes: 58687acb ("lockup_detector: Combine nmi_watchdog and softlockup detector")
Reported-and-tested-by: NKan Liang <Kan.liang@intel.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: dzickus@redhat.com
Cc: prarit@redhat.com
Cc: ak@linux.intel.com
Cc: babu.moger@oracle.com
Cc: peterz@infradead.org
Cc: eranian@google.com
Cc: acme@redhat.com
Cc: stable@vger.kernel.org
Cc: atomlin@redhat.com
Cc: akpm@linux-foundation.org
Cc: torvalds@linux-foundation.org
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1708150931310.1886@nanos
      7edaeb68
    • A
      x86: Constify attribute_group structures · 45bd07ad
      由 Arvind Yadav 提交于 
      attribute_groups are not supposed to change at runtime and none of the
groups is modified.

Mark the non-const structs as const.

[ tglx: Folded into one big patch ]
Signed-off-by: NArvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: tony.luck@intel.com
Cc: bp@alien8.de
Link: http://lkml.kernel.org/r/1500550238-15655-2-git-send-email-arvind.yadav.cs@gmail.com
      45bd07ad
  13. 17 8月, 2017 3 次提交
  15. 15 8月, 2017 2 次提交
  17. 11 8月, 2017 6 次提交
  19. 10 8月, 2017 10 次提交
  21. 09 8月, 2017 1 次提交
  23. 03 8月, 2017 2 次提交
    • W
      KVM: nVMX: Fix interrupt window request with "Acknowledge interrupt on exit" · 6550c4df
      由 Wanpeng Li 提交于 
      ------------[ cut here ]------------
 WARNING: CPU: 5 PID: 2288 at arch/x86/kvm/vmx.c:11124 nested_vmx_vmexit+0xd64/0xd70 [kvm_intel]
 CPU: 5 PID: 2288 Comm: qemu-system-x86 Not tainted 4.13.0-rc2+ #7
 RIP: 0010:nested_vmx_vmexit+0xd64/0xd70 [kvm_intel]
Call Trace:
  vmx_check_nested_events+0x131/0x1f0 [kvm_intel]
  ? vmx_check_nested_events+0x131/0x1f0 [kvm_intel]
  kvm_arch_vcpu_ioctl_run+0x5dd/0x1be0 [kvm]
  ? vmx_vcpu_load+0x1be/0x220 [kvm_intel]
  ? kvm_arch_vcpu_load+0x62/0x230 [kvm]
  kvm_vcpu_ioctl+0x340/0x700 [kvm]
  ? kvm_vcpu_ioctl+0x340/0x700 [kvm]
  ? __fget+0xfc/0x210
  do_vfs_ioctl+0xa4/0x6a0
  ? __fget+0x11d/0x210
  SyS_ioctl+0x79/0x90
  do_syscall_64+0x8f/0x750
  ? trace_hardirqs_on_thunk+0x1a/0x1c
  entry_SYSCALL64_slow_path+0x25/0x25

This can be reproduced by booting L1 guest w/ 'noapic' grub parameter, which
means that tells the kernel to not make use of any IOAPICs that may be present
in the system.

Actually external_intr variable in nested_vmx_vmexit() is the req_int_win
variable passed from vcpu_enter_guest() which means that the L0's userspace
requests an irq window. I observed the scenario (!kvm_cpu_has_interrupt(vcpu) &&
L0's userspace reqeusts an irq window) is true, so there is no interrupt which
L1 requires to inject to L2, we should not attempt to emualte "Acknowledge
interrupt on exit" for the irq window requirement in this scenario.

This patch fixes it by not attempt to emulate "Acknowledge interrupt on exit"
if there is no L1 requirement to inject an interrupt to L2.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
[Added code comment to make it obvious that the behavior is not correct.
 We should do a userspace exit with open interrupt window instead of the
 nested VM exit.  This patch still improves the behavior, so it was
 accepted as a (temporary) workaround.]
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
      6550c4df
    • D
      KVM: nVMX: mark vmcs12 pages dirty on L2 exit · c9f04407
      由 David Matlack 提交于 
      The host physical addresses of L1's Virtual APIC Page and Posted
Interrupt descriptor are loaded into the VMCS02. The CPU may write
to these pages via their host physical address while L2 is running,
bypassing address-translation-based dirty tracking (e.g. EPT write
protection). Mark them dirty on every exit from L2 to prevent them
from getting out of sync with dirty tracking.

Also mark the virtual APIC page and the posted interrupt descriptor
dirty when KVM is virtualizing posted interrupt processing.
Signed-off-by: NDavid Matlack <dmatlack@google.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
      c9f04407