From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
James Morse <james.morse@arm.com>, Will Deacon <will@kernel.org>,
Sasha Levin <sashal@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: [PATCH AUTOSEL 5.9 12/23] arm64: syscall: exit userspace before unmasking exceptions
Date: Sat, 12 Dec 2020 11:07:53 -0500 [thread overview]
Message-ID: <20201212160804.2334982-12-sashal@kernel.org> (raw)
In-Reply-To: <20201212160804.2334982-1-sashal@kernel.org>
From: Mark Rutland <mark.rutland@arm.com>
[ Upstream commit ca1314d73eed493c49bb1932c60a8605530db2e4 ]
In el0_svc_common() we unmask exceptions before we call user_exit(), and
so there's a window where an IRQ or debug exception can be taken while
RCU is not watching. In do_debug_exception() we account for this in via
debug_exception_{enter,exit}(), but in the el1_irq asm we do not and we
call trace functions which rely on RCU before we have a guarantee that
RCU is watching.
Let's avoid this by having el0_svc_common() exit userspace before
unmasking exceptions, matching what we do for all other EL0 entry paths.
We can use user_exit_irqoff() to avoid the pointless save/restore of IRQ
flags while we're sure exceptions are masked in DAIF.
The workaround for Cortex-A76 erratum 1463225 may trigger a debug
exception before this point, but the debug code invoked in this case is
safe even when RCU is not watching.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201130115950.22492-2-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/arm64/kernel/syscall.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index 5f0c04863d2c1..8a4bf00e538c3 100644
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -120,8 +120,8 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
*/
cortex_a76_erratum_1463225_svc_handler();
+ user_exit_irqoff();
local_daif_restore(DAIF_PROCCTX);
- user_exit();
if (has_syscall_work(flags)) {
/*
--
2.27.0
WARNING: multiple messages have this Message-ID (diff)
From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>,
Sasha Levin <sashal@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
James Morse <james.morse@arm.com>, Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: [PATCH AUTOSEL 5.9 12/23] arm64: syscall: exit userspace before unmasking exceptions
Date: Sat, 12 Dec 2020 11:07:53 -0500 [thread overview]
Message-ID: <20201212160804.2334982-12-sashal@kernel.org> (raw)
In-Reply-To: <20201212160804.2334982-1-sashal@kernel.org>
From: Mark Rutland <mark.rutland@arm.com>
[ Upstream commit ca1314d73eed493c49bb1932c60a8605530db2e4 ]
In el0_svc_common() we unmask exceptions before we call user_exit(), and
so there's a window where an IRQ or debug exception can be taken while
RCU is not watching. In do_debug_exception() we account for this in via
debug_exception_{enter,exit}(), but in the el1_irq asm we do not and we
call trace functions which rely on RCU before we have a guarantee that
RCU is watching.
Let's avoid this by having el0_svc_common() exit userspace before
unmasking exceptions, matching what we do for all other EL0 entry paths.
We can use user_exit_irqoff() to avoid the pointless save/restore of IRQ
flags while we're sure exceptions are masked in DAIF.
The workaround for Cortex-A76 erratum 1463225 may trigger a debug
exception before this point, but the debug code invoked in this case is
safe even when RCU is not watching.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201130115950.22492-2-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/arm64/kernel/syscall.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index 5f0c04863d2c1..8a4bf00e538c3 100644
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -120,8 +120,8 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
*/
cortex_a76_erratum_1463225_svc_handler();
+ user_exit_irqoff();
local_daif_restore(DAIF_PROCCTX);
- user_exit();
if (has_syscall_work(flags)) {
/*
--
2.27.0
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next prev parent reply other threads:[~2020-12-12 16:11 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-12 16:07 [PATCH AUTOSEL 5.9 01/23] drm/tegra: sor: Don't warn on probe deferral Sasha Levin
2020-12-12 16:07 ` Sasha Levin
2020-12-12 16:07 ` [PATCH AUTOSEL 5.9 02/23] drm/tegra: sor: Ensure regulators are disabled on teardown Sasha Levin
2020-12-12 16:07 ` Sasha Levin
2020-12-12 16:07 ` [PATCH AUTOSEL 5.9 03/23] drm/tegra: replace idr_init() by idr_init_base() Sasha Levin
2020-12-12 16:07 ` Sasha Levin
2020-12-12 16:07 ` [PATCH AUTOSEL 5.9 04/23] dm integrity: don't use drivers that have CRYPTO_ALG_ALLOCATES_MEMORY Sasha Levin
2020-12-12 16:07 ` [dm-devel] " Sasha Levin
2020-12-12 16:07 ` [PATCH AUTOSEL 5.9 05/23] gfs2: set lockdep subclass for iopen glocks Sasha Levin
2020-12-12 16:07 ` [Cluster-devel] " Sasha Levin
2020-12-12 16:07 ` [PATCH AUTOSEL 5.9 06/23] ASoC: rt5682: change SAR voltage threshold Sasha Levin
2020-12-12 16:07 ` Sasha Levin
2020-12-12 16:07 ` [PATCH AUTOSEL 5.9 07/23] kernel/cpu: add arch override for clear_tasks_mm_cpumask() mm handling Sasha Levin
2020-12-12 16:07 ` [PATCH AUTOSEL 5.9 08/23] drm/tegra: sor: Disable clocks on error in tegra_sor_init() Sasha Levin
2020-12-12 16:07 ` Sasha Levin
2020-12-12 16:07 ` [PATCH AUTOSEL 5.9 09/23] selftests: tc-testing: enable CONFIG_NET_SCH_RED as a module Sasha Levin
2020-12-12 16:07 ` [PATCH AUTOSEL 5.9 10/23] habanalabs: free host huge va_range if not used Sasha Levin
2020-12-12 16:07 ` [PATCH AUTOSEL 5.9 11/23] habanalabs: put devices before driver removal Sasha Levin
2020-12-12 16:07 ` Sasha Levin [this message]
2020-12-12 16:07 ` [PATCH AUTOSEL 5.9 12/23] arm64: syscall: exit userspace before unmasking exceptions Sasha Levin
2020-12-12 16:07 ` [PATCH AUTOSEL 5.9 13/23] vxlan: Add needed_headroom for lower device Sasha Levin
2020-12-12 16:07 ` [PATCH AUTOSEL 5.9 14/23] vxlan: Copy needed_tailroom from lowerdev Sasha Levin
2020-12-12 16:07 ` [PATCH AUTOSEL 5.9 15/23] scsi: storvsc: Validate length of incoming packet in storvsc_on_channel_callback() Sasha Levin
2020-12-12 16:07 ` Sasha Levin
2020-12-12 18:09 ` Andrea Parri
2020-12-12 18:09 ` Andrea Parri
2020-12-13 14:05 ` Sasha Levin
2020-12-13 14:05 ` Sasha Levin
2020-12-14 11:07 ` Dan Carpenter
2020-12-14 11:07 ` Dan Carpenter
2020-12-14 13:06 ` Konstantin Ryabitsev
2020-12-14 13:06 ` Konstantin Ryabitsev
2020-12-14 18:29 ` Sasha Levin
2020-12-14 18:29 ` Sasha Levin
2020-12-12 16:07 ` [PATCH AUTOSEL 5.9 16/23] scsi: mpt3sas: Increase IOCInit request timeout to 30s Sasha Levin
2020-12-12 16:07 ` [PATCH AUTOSEL 5.9 17/23] dm table: Remove BUG_ON(in_interrupt()) Sasha Levin
2020-12-12 16:07 ` [dm-devel] " Sasha Levin
2020-12-12 16:07 ` [PATCH AUTOSEL 5.9 18/23] iwlwifi: pcie: add one missing entry for AX210 Sasha Levin
2020-12-12 16:08 ` [PATCH AUTOSEL 5.9 19/23] iwlwifi: pcie: add some missing entries " Sasha Levin
2020-12-12 16:08 ` [PATCH AUTOSEL 5.9 20/23] drm/amd/display: Init clock value by current vbios CLKs Sasha Levin
2020-12-12 16:08 ` Sasha Levin
2020-12-12 16:08 ` [PATCH AUTOSEL 5.9 21/23] perf/x86/intel: Check PEBS status correctly Sasha Levin
2020-12-12 16:08 ` [PATCH AUTOSEL 5.9 22/23] kbuild: avoid split lines in .mod files Sasha Levin
2020-12-12 16:08 ` [PATCH AUTOSEL 5.9 23/23] tools/testing/selftests/vm: fix build error Sasha Levin
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