[PATCH v3 5/7] arm64: Handle faults caused by inadvertent user access with PAN enabled
From: catalin.marinas@arm.com (Catalin Marinas)
Date: 2016-09-13 17:46:35
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
When TTBR0_EL1 is set to the reserved page, an erroneous kernel access to user space would generate a translation fault. This patch adds the checks for the software-set PSR_PAN_BIT to emulate a permission fault and report it accordingly. This patch also updates the description of the synchronous external aborts on translation table walks. Cc: Will Deacon <redacted> Cc: James Morse <james.morse@arm.com> Cc: Kees Cook <redacted> Cc: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> --- arch/arm64/mm/fault.c | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-)
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 05d2bd776c69..2be46e6794e1 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c@@ -268,13 +268,19 @@ out: return fault; } -static inline bool is_permission_fault(unsigned int esr) +static inline bool is_permission_fault(unsigned int esr, struct pt_regs *regs) { unsigned int ec = ESR_ELx_EC(esr); unsigned int fsc_type = esr & ESR_ELx_FSC_TYPE; - return (ec == ESR_ELx_EC_DABT_CUR && fsc_type == ESR_ELx_FSC_PERM) || - (ec == ESR_ELx_EC_IABT_CUR && fsc_type == ESR_ELx_FSC_PERM); + if (ec != ESR_ELx_EC_DABT_CUR && ec != ESR_ELx_EC_IABT_CUR) + return false; + + if (system_uses_ttbr0_pan()) + return fsc_type == ESR_ELx_FSC_FAULT && + (regs->pstate & PSR_PAN_BIT); + else + return fsc_type == ESR_ELx_FSC_PERM; } static bool is_el0_instruction_abort(unsigned int esr)
@@ -314,7 +320,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, mm_flags |= FAULT_FLAG_WRITE; } - if (is_permission_fault(esr) && (addr < USER_DS)) { + if (addr < USER_DS && is_permission_fault(esr, regs)) { /* regs->orig_addr_limit may be 0 if we entered from EL0 */ if (regs->orig_addr_limit == KERNEL_DS) die("Accessing user space memory with fs=KERNEL_DS", regs, esr);
@@ -506,10 +512,10 @@ static const struct fault_info { { do_bad, SIGBUS, 0, "unknown 17" }, { do_bad, SIGBUS, 0, "unknown 18" }, { do_bad, SIGBUS, 0, "unknown 19" }, - { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, - { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, - { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, - { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, + { do_bad, SIGBUS, 0, "synchronous external abort (translation table walk)" }, + { do_bad, SIGBUS, 0, "synchronous external abort (translation table walk)" }, + { do_bad, SIGBUS, 0, "synchronous external abort (translation table walk)" }, + { do_bad, SIGBUS, 0, "synchronous external abort (translation table walk)" }, { do_bad, SIGBUS, 0, "synchronous parity error" }, { do_bad, SIGBUS, 0, "unknown 25" }, { do_bad, SIGBUS, 0, "unknown 26" },