leandrof/linux
1
0
Fork 0
forked from Minki/linux
Code Issues Pull Requests Packages Projects Releases Wiki Activity
6b88a32c7a
linux/arch/arm64
History
Catalin Marinas 6b88a32c7a arm64: kpti: Fix the interaction between ASID switching and software PAN 
With ARM64_SW_TTBR0_PAN enabled, the exception entry code checks the
active ASID to decide whether user access was enabled (non-zero ASID)
when the exception was taken. On return from exception, if user access
was previously disabled, it re-instates TTBR0_EL1 from the per-thread
saved value (updated in switch_mm() or efi_set_pgd()).

Commit 7655abb953 ("arm64: mm: Move ASID from TTBR0 to TTBR1") makes a
TTBR0_EL1 + ASID switching non-atomic. Subsequently, commit 27a921e757
("arm64: mm: Fix and re-enable ARM64_SW_TTBR0_PAN") changes the
__uaccess_ttbr0_disable() function and asm macro to first write the
reserved TTBR0_EL1 followed by the ASID=0 update in TTBR1_EL1. If an
exception occurs between these two, the exception return code will
re-instate a valid TTBR0_EL1. Similar scenario can happen in
cpu_switch_mm() between setting the reserved TTBR0_EL1 and the ASID
update in cpu_do_switch_mm().

This patch reverts the entry.S check for ASID == 0 to TTBR0_EL1 and
disables the interrupts around the TTBR0_EL1 and ASID switching code in
__uaccess_ttbr0_disable(). It also ensures that, when returning from the
EFI runtime services, efi_set_pgd() doesn't leave a non-zero ASID in
TTBR1_EL1 by using uaccess_ttbr0_{enable,disable}.

The accesses to current_thread_info()->ttbr0 are updated to use
READ_ONCE/WRITE_ONCE.

As a safety measure, __uaccess_ttbr0_enable() always masks out any
existing non-zero ASID TTBR1_EL1 before writing in the new ASID.

Fixes: 27a921e757 ("arm64: mm: Fix and re-enable ARM64_SW_TTBR0_PAN")
Acked-by: Will Deacon <will.deacon@arm.com>
Reported-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: James Morse <james.morse@arm.com>
Tested-by: James Morse <james.morse@arm.com>
Co-developed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2018-01-16 17:37:48 +00:00
..
boot Amlogic fixes for v4.15-rc 2017-12-09 20:23:29 -08:00
configs arm64: defconfig: enable CONFIG_GPIO_UNIPHIER 2017-10-30 14:41:54 +01:00
crypto License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
include arm64: kpti: Fix the interaction between ASID switching and software PAN 2018-01-16 17:37:48 +00:00
kernel arm64: kpti: Fix the interaction between ASID switching and software PAN 2018-01-16 17:37:48 +00:00
kvm KVM: arm64: Emulate RAS error registers and set HCR_EL2's TERR & TEA 2018-01-16 15:09:47 +00:00
lib arm64: kpti: Fix the interaction between ASID switching and software PAN 2018-01-16 17:37:48 +00:00
mm arm64: kpti: Fix the interaction between ASID switching and software PAN 2018-01-16 17:37:48 +00:00
net bpf, arm64: implement jiting of BPF_J{LT, LE, SLT, SLE} 2017-08-09 16:53:56 -07:00
xen arm64: kpti: Fix the interaction between ASID switching and software PAN 2018-01-16 17:37:48 +00:00
Kconfig arm64: cpufeature: Detect CPU RAS Extentions 2018-01-16 15:05:48 +00:00
Kconfig.debug arm64: relocation testing module 2017-04-04 17:03:32 +01:00
Kconfig.platforms ARM: SoC driver updates for v4.15 2017-11-16 16:05:01 -08:00
Makefile arm64: ftrace: emit ftrace-mod.o contents through code 2017-12-01 13:04:59 +00:00