From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Anand K Mistry <amistry@google.com>,
Borislav Petkov <bp@suse.de>
Subject: [PATCH 4.4 21/24] x86/speculation: Fix prctl() when spectre_v2_user={seccomp,prctl},ibpb
Date: Tue, 1 Dec 2020 09:53:27 +0100 [thread overview]
Message-ID: <20201201084638.819045957@linuxfoundation.org> (raw)
In-Reply-To: <20201201084637.754785180@linuxfoundation.org>
From: Anand K Mistry <amistry@google.com>
commit 33fc379df76b4991e5ae312f07bcd6820811971e upstream.
When spectre_v2_user={seccomp,prctl},ibpb is specified on the command
line, IBPB is force-enabled and STIPB is conditionally-enabled (or not
available).
However, since
21998a351512 ("x86/speculation: Avoid force-disabling IBPB based on STIBP and enhanced IBRS.")
the spectre_v2_user_ibpb variable is set to SPECTRE_V2_USER_{PRCTL,SECCOMP}
instead of SPECTRE_V2_USER_STRICT, which is the actual behaviour.
Because the issuing of IBPB relies on the switch_mm_*_ibpb static
branches, the mitigations behave as expected.
Since
1978b3a53a74 ("x86/speculation: Allow IBPB to be conditionally enabled on CPUs with always-on STIBP")
this discrepency caused the misreporting of IB speculation via prctl().
On CPUs with STIBP always-on and spectre_v2_user=seccomp,ibpb,
prctl(PR_GET_SPECULATION_CTRL) would return PR_SPEC_PRCTL |
PR_SPEC_ENABLE instead of PR_SPEC_DISABLE since both IBPB and STIPB are
always on. It also allowed prctl(PR_SET_SPECULATION_CTRL) to set the IB
speculation mode, even though the flag is ignored.
Similarly, for CPUs without SMT, prctl(PR_GET_SPECULATION_CTRL) should
also return PR_SPEC_DISABLE since IBPB is always on and STIBP is not
available.
[ bp: Massage commit message. ]
Fixes: 21998a351512 ("x86/speculation: Avoid force-disabling IBPB based on STIBP and enhanced IBRS.")
Fixes: 1978b3a53a74 ("x86/speculation: Allow IBPB to be conditionally enabled on CPUs with always-on STIBP")
Signed-off-by: Anand K Mistry <amistry@google.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20201110123349.1.Id0cbf996d2151f4c143c90f9028651a5b49a5908@changeid
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kernel/cpu/bugs.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -707,11 +707,13 @@ spectre_v2_user_select_mitigation(enum s
if (boot_cpu_has(X86_FEATURE_IBPB)) {
setup_force_cpu_cap(X86_FEATURE_USE_IBPB);
+ spectre_v2_user_ibpb = mode;
switch (cmd) {
case SPECTRE_V2_USER_CMD_FORCE:
case SPECTRE_V2_USER_CMD_PRCTL_IBPB:
case SPECTRE_V2_USER_CMD_SECCOMP_IBPB:
static_branch_enable(&switch_mm_always_ibpb);
+ spectre_v2_user_ibpb = SPECTRE_V2_USER_STRICT;
break;
case SPECTRE_V2_USER_CMD_PRCTL:
case SPECTRE_V2_USER_CMD_AUTO:
@@ -725,8 +727,6 @@ spectre_v2_user_select_mitigation(enum s
pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n",
static_key_enabled(&switch_mm_always_ibpb) ?
"always-on" : "conditional");
-
- spectre_v2_user_ibpb = mode;
}
/*
next prev parent reply other threads:[~2020-12-01 8:55 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-01 8:53 [PATCH 4.4 00/24] 4.4.247-rc1 review Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 01/24] btrfs: tree-checker: Enhance chunk checker to validate chunk profile Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 02/24] btrfs: inode: Verify inode mode to avoid NULL pointer dereference Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 03/24] KVM: x86: Fix split-irqchip vs interrupt injection window request Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 04/24] HID: cypress: Support Varmilo Keyboards media hotkeys Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 05/24] Input: i8042 - allow insmod to succeed on devices without an i8042 controller Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 06/24] HID: hid-sensor-hub: Fix issue with devices with no report ID Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 07/24] x86/xen: dont unbind uninitialized lock_kicker_irq Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 08/24] proc: dont allow async path resolution of /proc/self components Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 09/24] dmaengine: pl330: _prep_dma_memcpy: Fix wrong burst size Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 10/24] scsi: libiscsi: Fix NOP race condition Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 11/24] scsi: target: iscsi: Fix cmd abort fabric stop race Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 12/24] scsi: ufs: Fix race between shutdown and runtime resume flow Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 13/24] bnxt_en: fix error return code in bnxt_init_board() Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 14/24] video: hyperv_fb: Fix the cache type when mapping the VRAM Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 15/24] bnxt_en: Release PCI regions when DMA mask setup fails during probe Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 16/24] IB/mthca: fix return value of error branch in mthca_init_cq() Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 17/24] nfc: s3fwrn5: use signed integer for parsing GPIO numbers Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 18/24] efivarfs: revert "fix memory leak in efivarfs_create()" Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 19/24] perf probe: Fix to die_entrypc() returns error correctly Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 20/24] USB: core: Change %pK for __user pointers to %px Greg Kroah-Hartman
2020-12-01 8:53 ` Greg Kroah-Hartman [this message]
2020-12-01 8:53 ` [PATCH 4.4 22/24] USB: core: add endpoint-blacklist quirk Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 23/24] USB: core: Fix regression in Hercules audio card Greg Kroah-Hartman
2020-12-01 8:53 ` [PATCH 4.4 24/24] btrfs: fix lockdep splat when reading qgroup config on mount Greg Kroah-Hartman
2020-12-01 13:41 ` [PATCH 4.4 00/24] 4.4.247-rc1 review Jon Hunter
2020-12-01 15:59 ` Pavel Machek
2020-12-01 21:38 ` Guenter Roeck
2020-12-02 6:17 ` Naresh Kamboju
2020-12-02 17:04 ` Shuah Khan
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