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Commit e19a6ee2 authored by James Morse's avatar James Morse Committed by Will Deacon
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arm64: kernel: Save and restore UAO and addr_limit on exception entry 



If we take an exception while at EL1, the exception handler inherits
the original context's addr_limit and PSTATE.UAO values. To be consistent
always reset addr_limit and PSTATE.UAO on (re-)entry to EL1. This
prevents accidental re-use of the original context's addr_limit.

Based on a similar patch for arm from Russell King.

Cc: <stable@vger.kernel.org> # 4.6-
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Reviewed-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarJames Morse <james.morse@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 4c2e07c6

arch/arm64/include/asm/ptrace.h

+2 −0
Original line number Diff line number Diff line
@@ -117,6 +117,8 @@ struct pt_regs { 
	};

	u64 orig_x0;

	u64 syscallno;

	u64 orig_addr_limit;

	u64 unused;	// maintain 16 byte alignment

};



#define arch_has_single_step()	(1)

arch/arm64/kernel/asm-offsets.c

+1 −0
Original line number Diff line number Diff line
@@ -60,6 +60,7 @@ int main(void) 
  DEFINE(S_PC,			offsetof(struct pt_regs, pc));

  DEFINE(S_ORIG_X0,		offsetof(struct pt_regs, orig_x0));

  DEFINE(S_SYSCALLNO,		offsetof(struct pt_regs, syscallno));

  DEFINE(S_ORIG_ADDR_LIMIT,	offsetof(struct pt_regs, orig_addr_limit));

  DEFINE(S_FRAME_SIZE,		sizeof(struct pt_regs));

  BLANK();

  DEFINE(MM_CONTEXT_ID,		offsetof(struct mm_struct, context.id.counter));

arch/arm64/kernel/entry.S

+17 −2
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 
#include <asm/errno.h>

#include <asm/esr.h>

#include <asm/irq.h>

#include <asm/memory.h>

#include <asm/thread_info.h>

#include <asm/unistd.h>
@@ -97,7 +98,14 @@ 
	mov	x29, xzr			// fp pointed to user-space

	.else

	add	x21, sp, #S_FRAME_SIZE

	.endif

	get_thread_info tsk

	/* Save the task's original addr_limit and set USER_DS (TASK_SIZE_64) */

	ldr	x20, [tsk, #TI_ADDR_LIMIT]

	str	x20, [sp, #S_ORIG_ADDR_LIMIT]

	mov	x20, #TASK_SIZE_64

	str	x20, [tsk, #TI_ADDR_LIMIT]

	ALTERNATIVE(nop, SET_PSTATE_UAO(0), ARM64_HAS_UAO, CONFIG_ARM64_UAO)

	.endif /* \el == 0 */

	mrs	x22, elr_el1

	mrs	x23, spsr_el1

	stp	lr, x21, [sp, #S_LR]
@@ -128,6 +136,14 @@ 
	.endm



	.macro	kernel_exit, el

	.if	\el != 0

	/* Restore the task's original addr_limit. */

	ldr	x20, [sp, #S_ORIG_ADDR_LIMIT]

	str	x20, [tsk, #TI_ADDR_LIMIT]



	/* No need to restore UAO, it will be restored from SPSR_EL1 */

	.endif



	ldp	x21, x22, [sp, #S_PC]		// load ELR, SPSR

	.if	\el == 0

	ct_user_enter
@@ -406,7 +422,6 @@ el1_irq: 
	bl	trace_hardirqs_off

#endif



	get_thread_info tsk

	irq_handler



#ifdef CONFIG_PREEMPT

arch/arm64/mm/fault.c

+2 −1
Original line number Diff line number Diff line
@@ -280,7 +280,8 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, 
	}



	if (permission_fault(esr) && (addr < USER_DS)) {

		if (get_fs() == KERNEL_DS)

		/* 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);



		if (!search_exception_tables(regs->pc))