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When RDRAND was introduced, there was much discussion on whether it
should be trusted and how the kernel should handle that. Initially, two
mechanisms cropped up, CONFIG_ARCH_RANDOM, a compile time switch, and
"nordrand", a boot-time switch.
Later the thinking evolved. With a properly designed RNG, using RDRAND
values alone won't harm anything, even if the outputs are malicious.
Rather, the issue is whether those values are being *trusted* to be good
or not. And so a new set of options were introduced as the real
ones that people use -- CONFIG_RANDOM_TRUST_CPU and "random.trust_cpu".
With these options, RDRAND is used, but it's not always credited. So in
the worst case, it does nothing, and in the best case, maybe it helps.
Along the way, CONFIG_ARCH_RANDOM's meaning got sort of pulled into the
center and became something certain platforms force-select.
The old options don't really help with much, and it's a bit odd to have
special handling for these instructions when the kernel can deal fine
with the existence or untrusted existence or broken existence or
non-existence of that CPU capability.
Simplify the situation by removing CONFIG_ARCH_RANDOM and using the
ordinary asm-generic fallback pattern instead, keeping the two options
that are actually used. For now it leaves "nordrand" for now, as the
removal of that will take a different route.
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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When running with return thunks enabled under 32-bit EFI, the system
crashes with:
kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
BUG: unable to handle page fault for address: 000000005bc02900
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0011) - permissions violation
PGD 18f7063 P4D 18f7063 PUD 18ff063 PMD 190e063 PTE 800000005bc02063
Oops: 0011 [#1] PREEMPT SMP PTI
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.19.0-rc6+ #166
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
RIP: 0010:0x5bc02900
Code: Unable to access opcode bytes at RIP 0x5bc028d6.
RSP: 0018:ffffffffb3203e10 EFLAGS: 00010046
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000048
RDX: 000000000190dfac RSI: 0000000000001710 RDI: 000000007eae823b
RBP: ffffffffb3203e70 R08: 0000000001970000 R09: ffffffffb3203e28
R10: 747563657865206c R11: 6c6977203a696665 R12: 0000000000001710
R13: 0000000000000030 R14: 0000000001970000 R15: 0000000000000001
FS: 0000000000000000(0000) GS:ffff8e013ca00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0018 ES: 0018 CR0: 0000000080050033
CR2: 000000005bc02900 CR3: 0000000001930000 CR4: 00000000000006f0
Call Trace:
? efi_set_virtual_address_map+0x9c/0x175
efi_enter_virtual_mode+0x4a6/0x53e
start_kernel+0x67c/0x71e
x86_64_start_reservations+0x24/0x2a
x86_64_start_kernel+0xe9/0xf4
secondary_startup_64_no_verify+0xe5/0xeb
That's because it cannot jump to the return thunk from the 32-bit code.
Using a naked RET and marking it as safe allows the system to proceed
booting.
Fixes: aa3d480315ba ("x86: Use return-thunk in asm code")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: <stable@vger.kernel.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Pull KVM fixes from Paolo Bonzini:
"RISC-V:
- Fix missing PAGE_PFN_MASK
- Fix SRCU deadlock caused by kvm_riscv_check_vcpu_requests()
x86:
- Fix for nested virtualization when TSC scaling is active
- Estimate the size of fastcc subroutines conservatively, avoiding
disastrous underestimation when return thunks are enabled
- Avoid possible use of uninitialized fields of 'struct
kvm_lapic_irq'
Generic:
- Mark as such the boolean values available from the statistics file
descriptors
- Clarify statistics documentation"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
KVM: emulate: do not adjust size of fastop and setcc subroutines
KVM: x86: Fully initialize 'struct kvm_lapic_irq' in kvm_pv_kick_cpu_op()
Documentation: kvm: clarify histogram units
kvm: stats: tell userspace which values are boolean
x86/kvm: fix FASTOP_SIZE when return thunks are enabled
KVM: nVMX: Always enable TSC scaling for L2 when it was enabled for L1
RISC-V: KVM: Fix SRCU deadlock caused by kvm_riscv_check_vcpu_requests()
riscv: Fix missing PAGE_PFN_MASK
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Instead of doing complicated calculations to find the size of the subroutines
(which are even more complicated because they need to be stringified into
an asm statement), just hardcode to 16.
It is less dense for a few combinations of IBT/SLS/retbleed, but it has
the advantage of being really simple.
Cc: stable@vger.kernel.org # 5.15.x: 84e7051c0bc1: x86/kvm: fix FASTOP_SIZE when return thunks are enabled
Cc: stable@vger.kernel.org
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Clang warns:
arch/x86/kernel/cpu/bugs.c:58:21: error: section attribute is specified on redeclared variable [-Werror,-Wsection]
DEFINE_PER_CPU(u64, x86_spec_ctrl_current);
^
arch/x86/include/asm/nospec-branch.h:283:12: note: previous declaration is here
extern u64 x86_spec_ctrl_current;
^
1 error generated.
The declaration should be using DECLARE_PER_CPU instead so all
attributes stay in sync.
Cc: stable@vger.kernel.org
Fixes: fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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'vector' and 'trig_mode' fields of 'struct kvm_lapic_irq' are left
uninitialized in kvm_pv_kick_cpu_op(). While these fields are normally
not needed for APIC_DM_REMRD, they're still referenced by
__apic_accept_irq() for trace_kvm_apic_accept_irq(). Fully initialize
the structure to avoid consuming random stack memory.
Fixes: a183b638b61c ("KVM: x86: make apic_accept_irq tracepoint more generic")
Reported-by: syzbot+d6caa905917d353f0d07@syzkaller.appspotmail.com
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220708125147.593975-1-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Merge bugfix needed in both 5.19 (because it's bad) and 5.20 (because
it is a prerequisite to test new features).
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Some of the statistics values exported by KVM are always only 0 or 1.
It can be useful to export this fact to userspace so that it can track
them specially (for example by polling the value every now and then to
compute a % of time spent in a specific state).
Therefore, add "boolean value" as a new "unit". While it is not exactly
a unit, it walks and quacks like one. In particular, using the type
would be wrong because boolean values could be instantaneous or peak
values (e.g. "is the rmap allocated?") or even two-bucket histograms
(e.g. "number of posted vs. non-posted interrupt injections").
Suggested-by: Amneesh Singh <natto@weirdnatto.in>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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The return thunk call makes the fastop functions larger, just like IBT
does. Consider a 16-byte FASTOP_SIZE when CONFIG_RETHUNK is enabled.
Otherwise, functions will be incorrectly aligned and when computing their
position for differently sized operators, they will executed in the middle
or end of a function, which may as well be an int3, leading to a crash
like:
[ 36.091116] int3: 0000 [#1] SMP NOPTI
[ 36.091119] CPU: 3 PID: 1371 Comm: qemu-system-x86 Not tainted 5.15.0-41-generic #44
[ 36.091120] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014
[ 36.091121] RIP: 0010:xaddw_ax_dx+0x9/0x10 [kvm]
[ 36.091185] Code: 00 0f bb d0 c3 cc cc cc cc 48 0f bb d0 c3 cc cc cc cc 0f 1f 80 00 00 00 00 0f c0 d0 c3 cc cc cc cc 66 0f c1 d0 c3 cc cc cc cc <0f> 1f 80 00 00 00 00 0f c1 d0 c3 cc cc cc cc 48 0f c1 d0 c3 cc cc
[ 36.091186] RSP: 0018:ffffb1f541143c98 EFLAGS: 00000202
[ 36.091188] RAX: 0000000089abcdef RBX: 0000000000000001 RCX: 0000000000000000
[ 36.091188] RDX: 0000000076543210 RSI: ffffffffc073c6d0 RDI: 0000000000000200
[ 36.091189] RBP: ffffb1f541143ca0 R08: ffff9f1803350a70 R09: 0000000000000002
[ 36.091190] R10: ffff9f1803350a70 R11: 0000000000000000 R12: ffff9f1803350a70
[ 36.091190] R13: ffffffffc077fee0 R14: 0000000000000000 R15: 0000000000000000
[ 36.091191] FS: 00007efdfce8d640(0000) GS:ffff9f187dd80000(0000) knlGS:0000000000000000
[ 36.091192] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 36.091192] CR2: 0000000000000000 CR3: 0000000009b62002 CR4: 0000000000772ee0
[ 36.091195] PKRU: 55555554
[ 36.091195] Call Trace:
[ 36.091197] <TASK>
[ 36.091198] ? fastop+0x5a/0xa0 [kvm]
[ 36.091222] x86_emulate_insn+0x7b8/0xe90 [kvm]
[ 36.091244] x86_emulate_instruction+0x2f4/0x630 [kvm]
[ 36.091263] ? kvm_arch_vcpu_load+0x7c/0x230 [kvm]
[ 36.091283] ? vmx_prepare_switch_to_host+0xf7/0x190 [kvm_intel]
[ 36.091290] complete_emulated_mmio+0x297/0x320 [kvm]
[ 36.091310] kvm_arch_vcpu_ioctl_run+0x32f/0x550 [kvm]
[ 36.091330] kvm_vcpu_ioctl+0x29e/0x6d0 [kvm]
[ 36.091344] ? kvm_vcpu_ioctl+0x120/0x6d0 [kvm]
[ 36.091357] ? __fget_files+0x86/0xc0
[ 36.091362] ? __fget_files+0x86/0xc0
[ 36.091363] __x64_sys_ioctl+0x92/0xd0
[ 36.091366] do_syscall_64+0x59/0xc0
[ 36.091369] ? syscall_exit_to_user_mode+0x27/0x50
[ 36.091370] ? do_syscall_64+0x69/0xc0
[ 36.091371] ? syscall_exit_to_user_mode+0x27/0x50
[ 36.091372] ? __x64_sys_writev+0x1c/0x30
[ 36.091374] ? do_syscall_64+0x69/0xc0
[ 36.091374] ? exit_to_user_mode_prepare+0x37/0xb0
[ 36.091378] ? syscall_exit_to_user_mode+0x27/0x50
[ 36.091379] ? do_syscall_64+0x69/0xc0
[ 36.091379] ? do_syscall_64+0x69/0xc0
[ 36.091380] ? do_syscall_64+0x69/0xc0
[ 36.091381] ? do_syscall_64+0x69/0xc0
[ 36.091381] entry_SYSCALL_64_after_hwframe+0x61/0xcb
[ 36.091384] RIP: 0033:0x7efdfe6d1aff
[ 36.091390] Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <41> 89 c0 3d 00 f0 ff ff 77 1f 48 8b 44 24 18 64 48 2b 04 25 28 00
[ 36.091391] RSP: 002b:00007efdfce8c460 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[ 36.091393] RAX: ffffffffffffffda RBX: 000000000000ae80 RCX: 00007efdfe6d1aff
[ 36.091393] RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 000000000000000c
[ 36.091394] RBP: 0000558f1609e220 R08: 0000558f13fb8190 R09: 00000000ffffffff
[ 36.091394] R10: 0000558f16b5e950 R11: 0000000000000246 R12: 0000000000000000
[ 36.091394] R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000
[ 36.091396] </TASK>
[ 36.091397] Modules linked in: isofs nls_iso8859_1 kvm_intel joydev kvm input_leds serio_raw sch_fq_codel dm_multipath scsi_dh_rdac scsi_dh_emc scsi_dh_alua ipmi_devintf ipmi_msghandler drm msr ip_tables x_tables autofs4 btrfs blake2b_generic zstd_compress raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear crct10dif_pclmul crc32_pclmul ghash_clmulni_intel aesni_intel virtio_net net_failover crypto_simd ahci xhci_pci cryptd psmouse virtio_blk libahci xhci_pci_renesas failover
[ 36.123271] ---[ end trace db3c0ab5a48fabcc ]---
[ 36.123272] RIP: 0010:xaddw_ax_dx+0x9/0x10 [kvm]
[ 36.123319] Code: 00 0f bb d0 c3 cc cc cc cc 48 0f bb d0 c3 cc cc cc cc 0f 1f 80 00 00 00 00 0f c0 d0 c3 cc cc cc cc 66 0f c1 d0 c3 cc cc cc cc <0f> 1f 80 00 00 00 00 0f c1 d0 c3 cc cc cc cc 48 0f c1 d0 c3 cc cc
[ 36.123320] RSP: 0018:ffffb1f541143c98 EFLAGS: 00000202
[ 36.123321] RAX: 0000000089abcdef RBX: 0000000000000001 RCX: 0000000000000000
[ 36.123321] RDX: 0000000076543210 RSI: ffffffffc073c6d0 RDI: 0000000000000200
[ 36.123322] RBP: ffffb1f541143ca0 R08: ffff9f1803350a70 R09: 0000000000000002
[ 36.123322] R10: ffff9f1803350a70 R11: 0000000000000000 R12: ffff9f1803350a70
[ 36.123323] R13: ffffffffc077fee0 R14: 0000000000000000 R15: 0000000000000000
[ 36.123323] FS: 00007efdfce8d640(0000) GS:ffff9f187dd80000(0000) knlGS:0000000000000000
[ 36.123324] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 36.123325] CR2: 0000000000000000 CR3: 0000000009b62002 CR4: 0000000000772ee0
[ 36.123327] PKRU: 55555554
[ 36.123328] Kernel panic - not syncing: Fatal exception in interrupt
[ 36.123410] Kernel Offset: 0x1400000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
[ 36.135305] ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---
Fixes: aa3d480315ba ("x86: Use return-thunk in asm code")
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Co-developed-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Message-Id: <20220713171241.184026-1-cascardo@canonical.com>
Tested-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Windows 10/11 guests with Hyper-V role (WSL2) enabled are observed to
hang upon boot or shortly after when a non-default TSC frequency was
set for L1. The issue is observed on a host where TSC scaling is
supported. The problem appears to be that Windows doesn't use TSC
frequency for its guests even when the feature is advertised and KVM
filters SECONDARY_EXEC_TSC_SCALING out when creating L2 controls from
L1's. This leads to L2 running with the default frequency (matching
host's) while L1 is running with an altered one.
Keep SECONDARY_EXEC_TSC_SCALING in secondary exec controls for L2 when
it was set for L1. TSC_MULTIPLIER is already correctly computed and
written by prepare_vmcs02().
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20220712135009.952805-1-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull lockdep fix for x86 retbleed from Borislav Petkov:
- Fix lockdep complaint for __static_call_fixup()
* tag 'x86_bugs_retbleed' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/static_call: Serialize __static_call_fixup() properly
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__static_call_fixup() invokes __static_call_transform() without holding
text_mutex, which causes lockdep to complain in text_poke_bp().
Adding the proper locking cures that, but as this is either used during
early boot or during module finalizing, it's not required to use
text_poke_bp(). Add an argument to __static_call_transform() which tells
it to use text_poke_early() for it.
Fixes: ee88d363d156 ("x86,static_call: Use alternative RET encoding")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 retbleed fixes from Borislav Petkov:
"Just when you thought that all the speculation bugs were addressed and
solved and the nightmare is complete, here's the next one: speculating
after RET instructions and leaking privileged information using the
now pretty much classical covert channels.
It is called RETBleed and the mitigation effort and controlling
functionality has been modelled similar to what already existing
mitigations provide"
* tag 'x86_bugs_retbleed' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (54 commits)
x86/speculation: Disable RRSBA behavior
x86/kexec: Disable RET on kexec
x86/bugs: Do not enable IBPB-on-entry when IBPB is not supported
x86/entry: Move PUSH_AND_CLEAR_REGS() back into error_entry
x86/bugs: Add Cannon lake to RETBleed affected CPU list
x86/retbleed: Add fine grained Kconfig knobs
x86/cpu/amd: Enumerate BTC_NO
x86/common: Stamp out the stepping madness
KVM: VMX: Prevent RSB underflow before vmenter
x86/speculation: Fill RSB on vmexit for IBRS
KVM: VMX: Fix IBRS handling after vmexit
KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS
KVM: VMX: Convert launched argument to flags
KVM: VMX: Flatten __vmx_vcpu_run()
objtool: Re-add UNWIND_HINT_{SAVE_RESTORE}
x86/speculation: Remove x86_spec_ctrl_mask
x86/speculation: Use cached host SPEC_CTRL value for guest entry/exit
x86/speculation: Fix SPEC_CTRL write on SMT state change
x86/speculation: Fix firmware entry SPEC_CTRL handling
x86/speculation: Fix RSB filling with CONFIG_RETPOLINE=n
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fixes from Borislav Petkov:
- Prepare for and clear .brk early in order to address XenPV guests
failures where the hypervisor verifies page tables and uninitialized
data in that range leads to bogus failures in those checks
- Add any potential setup_data entries supplied at boot to the identity
pagetable mappings to prevent kexec kernel boot failures. Usually,
this is not a problem for the normal kernel as those mappings are
part of the initially mapped 2M pages but if kexec gets to allocate
the second kernel somewhere else, those setup_data entries need to be
mapped there too.
- Fix objtool not to discard text references from the __tracepoints
section so that ENDBR validation still works
- Correct the setup_data types limit as it is user-visible, before 5.19
releases
* tag 'x86_urgent_for_v5.19_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/boot: Fix the setup data types max limit
x86/ibt, objtool: Don't discard text references from tracepoint section
x86/compressed/64: Add identity mappings for setup_data entries
x86: Fix .brk attribute in linker script
x86: Clear .brk area at early boot
x86/xen: Use clear_bss() for Xen PV guests
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Commit in Fixes forgot to change the SETUP_TYPE_MAX definition which
contains the highest valid setup data type.
Correct that.
Fixes: 5ea98e01ab52 ("x86/boot: Add Confidential Computing type to setup_data")
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/ddba81dd-cc92-699c-5274-785396a17fb5@zytor.com
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Some Intel processors may use alternate predictors for RETs on
RSB-underflow. This condition may be vulnerable to Branch History
Injection (BHI) and intramode-BTI.
Kernel earlier added spectre_v2 mitigation modes (eIBRS+Retpolines,
eIBRS+LFENCE, Retpolines) which protect indirect CALLs and JMPs against
such attacks. However, on RSB-underflow, RET target prediction may
fallback to alternate predictors. As a result, RET's predicted target
may get influenced by branch history.
A new MSR_IA32_SPEC_CTRL bit (RRSBA_DIS_S) controls this fallback
behavior when in kernel mode. When set, RETs will not take predictions
from alternate predictors, hence mitigating RETs as well. Support for
this is enumerated by CPUID.7.2.EDX[RRSBA_CTRL] (bit2).
For spectre v2 mitigation, when a user selects a mitigation that
protects indirect CALLs and JMPs against BHI and intramode-BTI, set
RRSBA_DIS_S also to protect RETs for RSB-underflow case.
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
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All the invocations unroll to __x86_return_thunk and this file
must be PIC independent.
This fixes kexec on 64-bit AMD boxes.
[ bp: Fix 32-bit build. ]
Reported-by: Edward Tran <edward.tran@oracle.com>
Reported-by: Awais Tanveer <awais.tanveer@oracle.com>
Suggested-by: Ankur Arora <ankur.a.arora@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
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There are some VM configurations which have Skylake model but do not
support IBPB. In those cases, when using retbleed=ibpb, userspace is going
to be killed and kernel is going to panic.
If the CPU does not support IBPB, warn and proceed with the auto option. Also,
do not fallback to IBPB on AMD/Hygon systems if it is not supported.
Fixes: 3ebc17006888 ("x86/bugs: Add retbleed=ibpb")
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
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Commit
ee774dac0da1 ("x86/entry: Move PUSH_AND_CLEAR_REGS out of error_entry()")
moved PUSH_AND_CLEAR_REGS out of error_entry, into its own function, in
part to avoid calling error_entry() for XenPV.
However, commit
7c81c0c9210c ("x86/entry: Avoid very early RET")
had to change that because the 'ret' was too early and moved it into
idtentry, bloating the text size, since idtentry is expanded for every
exception vector.
However, with the advent of xen_error_entry() in commit
d147553b64bad ("x86/xen: Add UNTRAIN_RET")
it became possible to remove PUSH_AND_CLEAR_REGS from idtentry, back
into *error_entry().
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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Cannon lake is also affected by RETBleed, add it to the list.
Fixes: 6ad0ad2bf8a6 ("x86/bugs: Report Intel retbleed vulnerability")
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
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The decompressed kernel initially relies on the identity map set up by
the boot/compressed kernel for accessing things like boot_params. With
the recent introduction of SEV-SNP support, the decompressed kernel
also needs to access the setup_data entries pointed to by
boot_params->hdr.setup_data.
This can lead to a crash in the kexec kernel during early boot due to
these entries not currently being included in the initial identity map,
see thread at Link below.
Include mappings for the setup_data entries in the initial identity map.
[ bp: Massage commit message and use a helper var for better readability. ]
Fixes: b190a043c49a ("x86/sev: Add SEV-SNP feature detection/setup")
Reported-by: Jun'ichi Nomura <junichi.nomura@nec.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/TYCPR01MB694815CD815E98945F63C99183B49@TYCPR01MB6948.jpnprd01.prod.outlook.com
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commit 72f2ecb7ece7 ("ACPI: bus: Set CPPC _OSC bits for all and
when CPPC_LIB is supported") added support for claiming to
support CPPC in _OSC on non-Intel platforms.
This unfortunately caused a regression on a vartiety of AMD
platforms in the field because a number of AMD platforms don't set
the `_OSC` bit 5 or 6 to indicate CPPC or CPPC v2 support.
As these AMD platforms already claim CPPC support via a dedicated
MSR from `X86_FEATURE_CPPC`, use this enable this feature rather
than requiring the `_OSC` on platforms with a dedicated MSR.
If there is additional breakage on the shared memory designs also
missing this _OSC, additional follow up changes may be needed.
Fixes: 72f2ecb7ece7 ("Set CPPC _OSC bits for all and when CPPC_LIB is supported")
Reported-by: Perry Yuan <perry.yuan@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Commit in Fixes added the "NOLOAD" attribute to the .brk section as a
"failsafe" measure.
Unfortunately, this leads to the linker no longer covering the .brk
section in a program header, resulting in the kernel loader not knowing
that the memory for the .brk section must be reserved.
This has led to crashes when loading the kernel as PV dom0 under Xen,
but other scenarios could be hit by the same problem (e.g. in case an
uncompressed kernel is used and the initrd is placed directly behind
it).
So drop the "NOLOAD" attribute. This has been verified to correctly
cover the .brk section by a program header of the resulting ELF file.
Fixes: e32683c6f7d2 ("x86/mm: Fix RESERVE_BRK() for older binutils")
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/20220630071441.28576-4-jgross@suse.com
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The .brk section has the same properties as .bss: it is an alloc-only
section and should be cleared before being used.
Not doing so is especially a problem for Xen PV guests, as the
hypervisor will validate page tables (check for writable page tables
and hypervisor private bits) before accepting them to be used.
Make sure .brk is initially zero by letting clear_bss() clear the brk
area, too.
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220630071441.28576-3-jgross@suse.com
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Instead of clearing the bss area in assembly code, use the clear_bss()
function.
This requires to pass the start_info address as parameter to
xen_start_kernel() in order to avoid the xen_start_info being zeroed
again.
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20220630071441.28576-2-jgross@suse.com
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Do fine-grained Kconfig for all the various retbleed parts.
NOTE: if your compiler doesn't support return thunks this will
silently 'upgrade' your mitigation to IBPB, you might not like this.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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BTC_NO indicates that hardware is not susceptible to Branch Type Confusion.
Zen3 CPUs don't suffer BTC.
Hypervisors are expected to synthesise BTC_NO when it is appropriate
given the migration pool, to prevent kernels using heuristics.
[ bp: Massage. ]
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
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The whole MMIO/RETBLEED enumeration went overboard on steppings. Get
rid of all that and simply use ANY.
If a future stepping of these models would not be affected, it had
better set the relevant ARCH_CAP_$FOO_NO bit in
IA32_ARCH_CAPABILITIES.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
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On VMX, there are some balanced returns between the time the guest's
SPEC_CTRL value is written, and the vmenter.
Balanced returns (matched by a preceding call) are usually ok, but it's
at least theoretically possible an NMI with a deep call stack could
empty the RSB before one of the returns.
For maximum paranoia, don't allow *any* returns (balanced or otherwise)
between the SPEC_CTRL write and the vmenter.
[ bp: Fix 32-bit build. ]
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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Prevent RSB underflow/poisoning attacks with RSB. While at it, add a
bunch of comments to attempt to document the current state of tribal
knowledge about RSB attacks and what exactly is being mitigated.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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For legacy IBRS to work, the IBRS bit needs to be always re-written
after vmexit, even if it's already on.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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On eIBRS systems, the returns in the vmexit return path from
__vmx_vcpu_run() to vmx_vcpu_run() are exposed to RSB poisoning attacks.
Fix that by moving the post-vmexit spec_ctrl handling to immediately
after the vmexit.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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Convert __vmx_vcpu_run()'s 'launched' argument to 'flags', in
preparation for doing SPEC_CTRL handling immediately after vmexit, which
will need another flag.
This is much easier than adding a fourth argument, because this code
supports both 32-bit and 64-bit, and the fourth argument on 32-bit would
have to be pushed on the stack.
Note that __vmx_vcpu_run_flags() is called outside of the noinstr
critical section because it will soon start calling potentially
traceable functions.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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Move the vmx_vm{enter,exit}() functionality into __vmx_vcpu_run(). This
will make it easier to do the spec_ctrl handling before the first RET.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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Commit
c536ed2fffd5 ("objtool: Remove SAVE/RESTORE hints")
removed the save/restore unwind hints because they were no longer
needed. Now they're going to be needed again so re-add them.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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This mask has been made redundant by kvm_spec_ctrl_test_value(). And it
doesn't even work when MSR interception is disabled, as the guest can
just write to SPEC_CTRL directly.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
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There's no need to recalculate the host value for every entry/exit.
Just use the cached value in spec_ctrl_current().
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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If the SMT state changes, SSBD might get accidentally disabled. Fix
that.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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The firmware entry code may accidentally clear STIBP or SSBD. Fix that.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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If a kernel is built with CONFIG_RETPOLINE=n, but the user still wants
to mitigate Spectre v2 using IBRS or eIBRS, the RSB filling will be
silently disabled.
There's nothing retpoline-specific about RSB buffer filling. Remove the
CONFIG_RETPOLINE guards around it.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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Zen2 uarchs have an undocumented, unnamed, MSR that contains a chicken
bit for some speculation behaviour. It needs setting.
Note: very belatedly AMD released naming; it's now officially called
MSR_AMD64_DE_CFG2 and MSR_AMD64_DE_CFG2_SUPPRESS_NOBR_PRED_BIT
but shall remain the SPECTRAL CHICKEN.
Suggested-by: Andrew Cooper <Andrew.Cooper3@citrix.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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Since entry asm is tricky, add a validation pass that ensures the
retbleed mitigation has been done before the first actual RET
instruction.
Entry points are those that either have UNWIND_HINT_ENTRY, which acts
as UNWIND_HINT_EMPTY but marks the instruction as an entry point, or
those that have UWIND_HINT_IRET_REGS at +0.
This is basically a variant of validate_branch() that is
intra-function and it will simply follow all branches from marked
entry points and ensures that all paths lead to ANNOTATE_UNRET_END.
If a path hits RET or an indirection the path is a fail and will be
reported.
There are 3 ANNOTATE_UNRET_END instances:
- UNTRAIN_RET itself
- exception from-kernel; this path doesn't need UNTRAIN_RET
- all early exceptions; these also don't need UNTRAIN_RET
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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When booting with retbleed=auto, if the kernel wasn't built with
CONFIG_CC_HAS_RETURN_THUNK, the mitigation falls back to IBPB. Make
sure a warning is printed in that case. The IBPB fallback check is done
twice, but it really only needs to be done once.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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jmp2ret mitigates the easy-to-attack case at relatively low overhead.
It mitigates the long speculation windows after a mispredicted RET, but
it does not mitigate the short speculation window from arbitrary
instruction boundaries.
On Zen2, there is a chicken bit which needs setting, which mitigates
"arbitrary instruction boundaries" down to just "basic block boundaries".
But there is no fix for the short speculation window on basic block
boundaries, other than to flush the entire BTB to evict all attacker
predictions.
On the spectrum of "fast & blurry" -> "safe", there is (on top of STIBP
or no-SMT):
1) Nothing System wide open
2) jmp2ret May stop a script kiddy
3) jmp2ret+chickenbit Raises the bar rather further
4) IBPB Only thing which can count as "safe".
Tentative numbers put IBPB-on-entry at a 2.5x hit on Zen2, and a 10x hit
on Zen1 according to lmbench.
[ bp: Fixup feature bit comments, document option, 32-bit build fix. ]
Suggested-by: Andrew Cooper <Andrew.Cooper3@citrix.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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Ensure the Xen entry also passes through UNTRAIN_RET.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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Native SYS{CALL,ENTER} entry points are called
entry_SYS{CALL,ENTER}_{64,compat}, make sure the Xen versions are
named consistently.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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Update retpoline validation with the new CONFIG_RETPOLINE requirement of
not having bare naked RET instructions.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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Having IBRS enabled while the SMT sibling is idle unnecessarily slows
down the running sibling. OTOH, disabling IBRS around idle takes two
MSR writes, which will increase the idle latency.
Therefore, only disable IBRS around deeper idle states. Shallow idle
states are bounded by the tick in duration, since NOHZ is not allowed
for them by virtue of their short target residency.
Only do this for mwait-driven idle, since that keeps interrupts disabled
across idle, which makes disabling IBRS vs IRQ-entry a non-issue.
Note: C6 is a random threshold, most importantly C1 probably shouldn't
disable IBRS, benchmarking needed.
Suggested-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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Skylake suffers from RSB underflow speculation issues; report this
vulnerability and it's mitigation (spectre_v2=ibrs).
[jpoimboe: cleanups, eibrs]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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spectre_v2_user_select_mitigation()
retbleed will depend on spectre_v2, while spectre_v2_user depends on
retbleed. Break this cycle.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
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