Re: [PATCH 1/1] Fix: arm: kprobes: optimized kprobes illegal instruction

[Mathieu Desnoyers]

----- On Feb 5, 2019, at 10:04 AM, Kees Cook keescook@xxxxxxxxxxxx wrote:

> On Mon, Feb 4, 2019 at 9:52 PM Mathieu Desnoyers
> <mathieu.desnoyers@xxxxxxxxxxxx> wrote:
>>
>> commit e46daee53bb5 "ARM: 8806/1: kprobes: Fix false positive with
>> FORTIFY_SOURCE"
>> introduced a regression in optimized kprobes. It triggers "invalid
>> instruction" oopses when using kprobes instrumentation through lttng and
>> perf. This commit was introduced in kernel v4.20, and has been backported
>> to stable kernels 4.19 and 4.14.
>>
>> This crash was also reported by Hongzhi Song on the redhat bugzilla
>> where the patch was originally introduced.
> 
> Ew, yes. Thanks for catching this.
> 
> Fixes: e46daee53bb5 ("ARM: 8806/1: kprobes: Fix false positive with
> FORTIFY_SOURCE")
> Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
> 
> Can you send this to the ARM patch tracker, please?

Sure, will do right away,

Thanks!

Mathieu

> 
> -Kees
> 
>>
>> Link: https://bugzilla.redhat.com/show_bug.cgi?id=1639397
>> Link: https://bugs.lttng.org/issues/1174
>> Link:
>> https://lore.kernel.org/lkml/342740659.2887.1549307721609.JavaMail.zimbra@xxxxxxxxxxxx
>> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
>> Reported-by: Robert Berger <Robert.Berger@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
>> Tested-by: Robert Berger <Robert.Berger@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
>> CC: Robert Berger <Robert.Berger@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
>> CC: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
>> CC: William Cohen <wcohen@xxxxxxxxxx>
>> CC: Laura Abbott <labbott@xxxxxxxxxx>
>> CC: Kees Cook <keescook@xxxxxxxxxxxx>
>> CC: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
>> CC: <stable@xxxxxxxxxxxxxxx> # v4.14+
>> ---
>>  arch/arm/probes/kprobes/opt-arm.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/probes/kprobes/opt-arm.c
>> b/arch/arm/probes/kprobes/opt-arm.c
>> index 2c118a6ab358..0dc23fc227ed 100644
>> --- a/arch/arm/probes/kprobes/opt-arm.c
>> +++ b/arch/arm/probes/kprobes/opt-arm.c
>> @@ -247,7 +247,7 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe
>> *op, struct kprobe *or
>>         }
>>
>>         /* Copy arch-dep-instance from template. */
>> -       memcpy(code, (unsigned char *)optprobe_template_entry,
>> +       memcpy(code, (unsigned long *)&optprobe_template_entry,
>>                         TMPL_END_IDX * sizeof(kprobe_opcode_t));
>>
>>         /* Adjust buffer according to instruction. */
>> --
>> 2.11.0
>>
> 
> 
> --
> Kees Cook

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com