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Commit 27b729ba authored by Catalin Marinas's avatar Catalin Marinas Committed by Sami Tolvanen
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UPSTREAM: arm64: Handle faults caused by inadvertent user access with PAN enabled 



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.

Cc: Will Deacon <will.deacon@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>

Bug: 31432001
Change-Id: Ic280f88363f386b0d0e0ff276d211be95d1c7697
(cherry picked from commit 786889636ad75296c213547d1ca656af4c59f390)
Signed-off-by: default avatarSami Tolvanen <samitolvanen@google.com>
parent cfa93772

arch/arm64/mm/fault.c

+10 −4
Original line number Diff line number Diff line
@@ -269,13 +269,19 @@ static int __do_page_fault(struct mm_struct *mm, unsigned long addr, 
	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)
@@ -315,7 +321,7 @@ 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);