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arm64: mte: Ensure TIF_MTE_ASYNC_FAULT is set atomically

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The entry from EL0 code checks the TFSRE0_EL1 register for any
asynchronous tag check faults in user space and sets the
TIF_MTE_ASYNC_FAULT flag. This is not done atomically, potentially
racing with another CPU calling set_tsk_thread_flag().

Replace the non-atomic ORR+STR with an STSET instruction. While STSET
requires ARMv8.1 and an assembler that understands LSE atomics, the MTE
feature is part of ARMv8.5 and already requires an updated assembler.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Fixes: 637ec831ea ("arm64: mte: Handle synchronous and asynchronous tag check faults")
Cc: <stable@vger.kernel.org> # 5.10.x
Reported-by: Will Deacon <will@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20210409173710.18582-1-catalin.marinas@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Catalin Marinas 2021-04-09 18:37:10 +01:00 committed by Will Deacon
parent 185f2e5f51
commit 2decad92f4
2 changed files with 11 additions and 5 deletions
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6
arch/arm64/Kconfig
View File

@ -1406,10 +1406,13 @@ config ARM64_PAN
config AS_HAS_LDAPR
def_bool $(as-instr,.arch_extension rcpc)
config AS_HAS_LSE_ATOMICS
def_bool $(as-instr,.arch_extension lse)
config ARM64_LSE_ATOMICS
bool
default ARM64_USE_LSE_ATOMICS
depends on $(as-instr,.arch_extension lse)
depends on AS_HAS_LSE_ATOMICS
config ARM64_USE_LSE_ATOMICS
bool "Atomic instructions"
@ -1666,6 +1669,7 @@ config ARM64_MTE
default y
depends on ARM64_AS_HAS_MTE && ARM64_TAGGED_ADDR_ABI
depends on AS_HAS_ARMV8_5
depends on AS_HAS_LSE_ATOMICS
# Required for tag checking in the uaccess routines
depends on ARM64_PAN
select ARCH_USES_HIGH_VMA_FLAGS

10
arch/arm64/kernel/entry.S
View File

@ -148,16 +148,18 @@ alternative_cb_end
.endm
/* Check for MTE asynchronous tag check faults */
.macro check_mte_async_tcf, flgs, tmp
.macro check_mte_async_tcf, tmp, ti_flags
#ifdef CONFIG_ARM64_MTE
.arch_extension lse
alternative_if_not ARM64_MTE
b 1f
alternative_else_nop_endif
mrs_s \tmp, SYS_TFSRE0_EL1
tbz \tmp, #SYS_TFSR_EL1_TF0_SHIFT, 1f
/* Asynchronous TCF occurred for TTBR0 access, set the TI flag */
orr \flgs, \flgs, #_TIF_MTE_ASYNC_FAULT
str \flgs, [tsk, #TSK_TI_FLAGS]
mov \tmp, #_TIF_MTE_ASYNC_FAULT
add \ti_flags, tsk, #TSK_TI_FLAGS
stset \tmp, [\ti_flags]
msr_s SYS_TFSRE0_EL1, xzr
1:
#endif
@ -244,7 +246,7 @@ alternative_else_nop_endif
disable_step_tsk x19, x20
/* Check for asynchronous tag check faults in user space */
check_mte_async_tcf x19, x22
check_mte_async_tcf x22, x23
apply_ssbd 1, x22, x23
ptrauth_keys_install_kernel tsk, x20, x22, x23