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arm64: kernel: Save and restore UAO and addr_limit on exception entry

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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: Will Deacon <will.deacon@arm.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
James Morse 2016-06-20 18:28:01 +01:00 committed by Will Deacon
parent 4c2e07c6a2
commit e19a6ee246
4 changed files with 22 additions and 3 deletions
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2
arch/arm64/include/asm/ptrace.h
View File

@ -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)

1
arch/arm64/kernel/asm-offsets.c
View File

@ -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));

19
arch/arm64/kernel/entry.S
View File

@ -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

3
arch/arm64/mm/fault.c
View File

@ -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))