* [PATCH] ARM: kprobes: Fix false positive with FORTIFY_SOURCE
@ 2018-10-22 9:30 Kees Cook
2018-10-22 10:30 ` Laura Abbott
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Kees Cook @ 2018-10-22 9:30 UTC (permalink / raw)
To: Russell King
Cc: William Cohen, Laura Abbott, linux-kernel, Masami Hiramatsu,
linux-arm-kernel
The arm compiler internally interprets an inline assembly label
as an unsigned long value, not a pointer. As a result, under
CONFIG_FORTIFY_SOURCE, the size of the array pointed to by an address
of a label is 4 bytes, which was tripping the runtime checks. Instead,
we can just cast the label (as done with the size calculations earlier)
to avoid the problem.
Reported-by: William Cohen <wcohen@redhat.com>
Fixes: 6974f0c4555e ("include/linux/string.h: add the option of fortified string.h functions")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
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 b2aa9b32bff2..2c118a6ab358 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, &optprobe_template_entry,
+ memcpy(code, (unsigned char *)optprobe_template_entry,
TMPL_END_IDX * sizeof(kprobe_opcode_t));
/* Adjust buffer according to instruction. */
--
2.17.1
--
Kees Cook
Pixel Security
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] ARM: kprobes: Fix false positive with FORTIFY_SOURCE
2018-10-22 9:30 [PATCH] ARM: kprobes: Fix false positive with FORTIFY_SOURCE Kees Cook
@ 2018-10-22 10:30 ` Laura Abbott
2018-10-23 1:06 ` Masami Hiramatsu
2018-10-30 17:40 ` William Cohen
2 siblings, 0 replies; 6+ messages in thread
From: Laura Abbott @ 2018-10-22 10:30 UTC (permalink / raw)
To: Kees Cook, Russell King
Cc: William Cohen, linux-kernel, Masami Hiramatsu, linux-arm-kernel
On 10/22/2018 02:30 AM, Kees Cook wrote:
> The arm compiler internally interprets an inline assembly label
> as an unsigned long value, not a pointer. As a result, under
> CONFIG_FORTIFY_SOURCE, the size of the array pointed to by an address
> of a label is 4 bytes, which was tripping the runtime checks. Instead,
> we can just cast the label (as done with the size calculations earlier)
> to avoid the problem.
>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1639397
Acked-by: Laura Abbott <labbott@redhat.com>
> Reported-by: William Cohen <wcohen@redhat.com>
> Fixes: 6974f0c4555e ("include/linux/string.h: add the option of fortified string.h functions")
> Cc: stable@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> 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 b2aa9b32bff2..2c118a6ab358 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, &optprobe_template_entry,
> + memcpy(code, (unsigned char *)optprobe_template_entry,
> TMPL_END_IDX * sizeof(kprobe_opcode_t));
>
> /* Adjust buffer according to instruction. */
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] ARM: kprobes: Fix false positive with FORTIFY_SOURCE
2018-10-22 9:30 [PATCH] ARM: kprobes: Fix false positive with FORTIFY_SOURCE Kees Cook
2018-10-22 10:30 ` Laura Abbott
@ 2018-10-23 1:06 ` Masami Hiramatsu
2018-10-30 17:40 ` William Cohen
2 siblings, 0 replies; 6+ messages in thread
From: Masami Hiramatsu @ 2018-10-23 1:06 UTC (permalink / raw)
To: Kees Cook
Cc: Russell King, William Cohen, Laura Abbott, linux-kernel,
Masami Hiramatsu, linux-arm-kernel
On Mon, 22 Oct 2018 02:30:23 -0700
Kees Cook <keescook@chromium.org> wrote:
> The arm compiler internally interprets an inline assembly label
> as an unsigned long value, not a pointer. As a result, under
> CONFIG_FORTIFY_SOURCE, the size of the array pointed to by an address
> of a label is 4 bytes, which was tripping the runtime checks. Instead,
> we can just cast the label (as done with the size calculations earlier)
> to avoid the problem.
>
> Reported-by: William Cohen <wcohen@redhat.com>
> Fixes: 6974f0c4555e ("include/linux/string.h: add the option of fortified string.h functions")
> Cc: stable@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
Good catch! This looks good to me.
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Thank you,
> ---
> 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 b2aa9b32bff2..2c118a6ab358 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, &optprobe_template_entry,
> + memcpy(code, (unsigned char *)optprobe_template_entry,
> TMPL_END_IDX * sizeof(kprobe_opcode_t));
>
> /* Adjust buffer according to instruction. */
> --
> 2.17.1
>
>
> --
> Kees Cook
> Pixel Security
--
Masami Hiramatsu <mhiramat@kernel.org>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] ARM: kprobes: Fix false positive with FORTIFY_SOURCE
2018-10-22 9:30 [PATCH] ARM: kprobes: Fix false positive with FORTIFY_SOURCE Kees Cook
2018-10-22 10:30 ` Laura Abbott
2018-10-23 1:06 ` Masami Hiramatsu
@ 2018-10-30 17:40 ` William Cohen
2018-11-01 14:41 ` Masami Hiramatsu
2 siblings, 1 reply; 6+ messages in thread
From: William Cohen @ 2018-10-30 17:40 UTC (permalink / raw)
To: Kees Cook, Russell King
Cc: Laura Abbott, linux-kernel, Masami Hiramatsu, linux-arm-kernel
On 10/22/18 5:30 AM, Kees Cook wrote:
> The arm compiler internally interprets an inline assembly label
> as an unsigned long value, not a pointer. As a result, under
> CONFIG_FORTIFY_SOURCE, the size of the array pointed to by an address
> of a label is 4 bytes, which was tripping the runtime checks. Instead,
> we can just cast the label (as done with the size calculations earlier)
> to avoid the problem.
>
> Reported-by: William Cohen <wcohen@redhat.com>
> Fixes: 6974f0c4555e ("include/linux/string.h: add the option of fortified string.h functions")
> Cc: stable@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> 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 b2aa9b32bff2..2c118a6ab358 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, &optprobe_template_entry,
> + memcpy(code, (unsigned char *)optprobe_template_entry,
> TMPL_END_IDX * sizeof(kprobe_opcode_t));
>
> /* Adjust buffer according to instruction. */
>
The patch fixes the issue for kretprobes. It looks good to me.
Thanks,
-Will
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] ARM: kprobes: Fix false positive with FORTIFY_SOURCE
2018-10-30 17:40 ` William Cohen
@ 2018-11-01 14:41 ` Masami Hiramatsu
2018-11-01 20:53 ` Kees Cook
0 siblings, 1 reply; 6+ messages in thread
From: Masami Hiramatsu @ 2018-11-01 14:41 UTC (permalink / raw)
To: William Cohen
Cc: Kees Cook, Russell King, Laura Abbott, linux-kernel,
Masami Hiramatsu, linux-arm-kernel
On Tue, 30 Oct 2018 13:40:27 -0400
William Cohen <wcohen@redhat.com> wrote:
> On 10/22/18 5:30 AM, Kees Cook wrote:
> > The arm compiler internally interprets an inline assembly label
> > as an unsigned long value, not a pointer. As a result, under
> > CONFIG_FORTIFY_SOURCE, the size of the array pointed to by an address
> > of a label is 4 bytes, which was tripping the runtime checks. Instead,
> > we can just cast the label (as done with the size calculations earlier)
> > to avoid the problem.
> >
> > Reported-by: William Cohen <wcohen@redhat.com>
> > Fixes: 6974f0c4555e ("include/linux/string.h: add the option of fortified string.h functions")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> > 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 b2aa9b32bff2..2c118a6ab358 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, &optprobe_template_entry,
> > + memcpy(code, (unsigned char *)optprobe_template_entry,
> > TMPL_END_IDX * sizeof(kprobe_opcode_t));
> >
> > /* Adjust buffer according to instruction. */
> >
>
> The patch fixes the issue for kretprobes. It looks good to me.
This looks good to me too. Thank you for finding and fixing it :)
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Thanks!
>
> Thanks,
>
> -Will
--
Masami Hiramatsu <mhiramat@kernel.org>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] ARM: kprobes: Fix false positive with FORTIFY_SOURCE
2018-11-01 14:41 ` Masami Hiramatsu
@ 2018-11-01 20:53 ` Kees Cook
0 siblings, 0 replies; 6+ messages in thread
From: Kees Cook @ 2018-11-01 20:53 UTC (permalink / raw)
To: Masami Hiramatsu
Cc: William Cohen, Russell King, Laura Abbott, LKML, linux-arm-kernel
On Thu, Nov 1, 2018 at 7:41 AM, Masami Hiramatsu <mhiramat@kernel.org> wrote:
> On Tue, 30 Oct 2018 13:40:27 -0400
> William Cohen <wcohen@redhat.com> wrote:
>
>> On 10/22/18 5:30 AM, Kees Cook wrote:
>> > The arm compiler internally interprets an inline assembly label
>> > as an unsigned long value, not a pointer. As a result, under
>> > CONFIG_FORTIFY_SOURCE, the size of the array pointed to by an address
>> > of a label is 4 bytes, which was tripping the runtime checks. Instead,
>> > we can just cast the label (as done with the size calculations earlier)
>> > to avoid the problem.
>> >
>> > Reported-by: William Cohen <wcohen@redhat.com>
>> > Fixes: 6974f0c4555e ("include/linux/string.h: add the option of fortified string.h functions")
>> > Cc: stable@vger.kernel.org
>> > Signed-off-by: Kees Cook <keescook@chromium.org>
>> > ---
>> > 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 b2aa9b32bff2..2c118a6ab358 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, &optprobe_template_entry,
>> > + memcpy(code, (unsigned char *)optprobe_template_entry,
>> > TMPL_END_IDX * sizeof(kprobe_opcode_t));
>> >
>> > /* Adjust buffer according to instruction. */
>> >
>>
>> The patch fixes the issue for kretprobes. It looks good to me.
>
> This looks good to me too. Thank you for finding and fixing it :)
>
> Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
>
> Thanks!
Thanks for acks and testing. I've tossed this at the arm patch tracker:
http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=8806/1
--
Kees Cook
^ permalink raw reply [flat|nested] 6+ messages in thread
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2018-10-22 9:30 [PATCH] ARM: kprobes: Fix false positive with FORTIFY_SOURCE Kees Cook
2018-10-22 10:30 ` Laura Abbott
2018-10-23 1:06 ` Masami Hiramatsu
2018-10-30 17:40 ` William Cohen
2018-11-01 14:41 ` Masami Hiramatsu
2018-11-01 20:53 ` Kees Cook
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