On Wed, Apr 5, 2017 at 7:22 AM, Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > On Tue, Apr 04, 2017 at 10:47:27AM -0700, Thomas Garnier wrote: >> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S >> index 43512d4d7df2..6d598e7051c3 100644 >> --- a/arch/arm64/kernel/entry.S >> +++ b/arch/arm64/kernel/entry.S >> @@ -744,6 +744,10 @@ ENDPROC(cpu_switch_to) >> ret_fast_syscall: >> disable_irq // disable interrupts >> str x0, [sp, #S_X0] // returned x0 >> + ldr x2, [tsk, #TSK_TI_ADDR_LIMIT] // check addr limit change >> + mov x1, #TASK_SIZE_64 >> + cmp x2, x1 >> + b.ne addr_limit_fail > > KERNEL_DS is set to the maximum address (-1UL), so it would be easier to > check against this here and avoid a "mov". Even simpler if you'd check > against bit 63 of the address for KERNEL_DS: We also want to catch corruption so checking the 63 bit make sense. I will look for this change in the next iteration. > > ldr x1, [tsk, TSK_TI_ADDR_LIMIT] // check addr limit change > tbnz x1, #63, addr_limit_fail // KERNEL_DS is -1UL > >> ldr x1, [tsk, #TSK_TI_FLAGS] // re-check for syscall tracing >> and x2, x1, #_TIF_SYSCALL_WORK >> cbnz x2, ret_fast_syscall_trace >> @@ -771,6 +775,11 @@ work_pending: >> */ >> ret_to_user: >> disable_irq // disable interrupts >> + ldr x2, [tsk, #TSK_TI_ADDR_LIMIT] // check addr limit change >> + mov x1, #TASK_SIZE_64 >> + cmp x2, x1 >> + b.ne addr_limit_fail > > Same here. > >> + >> ldr x1, [tsk, #TSK_TI_FLAGS] >> and x2, x1, #_TIF_WORK_MASK >> cbnz x2, work_pending >> @@ -779,6 +788,12 @@ finish_ret_to_user: >> kernel_exit 0 >> ENDPROC(ret_to_user) >> >> +addr_limit_fail: >> + stp x0, lr, [sp,#-16]! >> + bl asm_verify_pre_usermode_state >> + ldp x0, lr, [sp],#16 >> + ret lr > > Where is this supposed to return? What is the value of lr when branching > to addr_limit_fail? It is not supposed to return. Do you think I should remove stp, ldp, ret and jut add a brk 0x100 or jmp/call a break/bug function? > > -- > Catalin -- Thomas -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
