From: Catalin Marinas catalin.marinas@arm.com
commit 2decad92f4731fac9755a083fcfefa66edb7d67d upstream.
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: 637ec831ea4f ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/Kconfig | 6 +++++- arch/arm64/kernel/entry.S | 10 ++++++---- 2 files changed, 11 insertions(+), 5 deletions(-)
--- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1399,10 +1399,13 @@ 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" @@ -1659,6 +1662,7 @@ 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 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -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