* [PATCH] randstruct: fix a bug in is_pure_ops_struct()
@ 2019-07-27 15:58 Joonwon Kang
2019-07-30 17:11 ` Kees Cook
0 siblings, 1 reply; 3+ messages in thread
From: Joonwon Kang @ 2019-07-27 15:58 UTC (permalink / raw)
To: keescook; +Cc: re.emese, kernel-hardening, linux-kernel, kernel-janitors
Before this, there were false negatives in the case where a struct
contains other structs which contain only function pointers because
of unreachable code in is_pure_ops_struct().
Signed-off-by: Joonwon Kang <kjw1627@gmail.com>
---
scripts/gcc-plugins/randomize_layout_plugin.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
diff --git a/scripts/gcc-plugins/randomize_layout_plugin.c b/scripts/gcc-plugins/randomize_layout_plugin.c
index 6d5bbd31db7f..a123282a4fcd 100644
--- a/scripts/gcc-plugins/randomize_layout_plugin.c
+++ b/scripts/gcc-plugins/randomize_layout_plugin.c
@@ -443,13 +443,12 @@ static int is_pure_ops_struct(const_tree node)
if (node == fieldtype)
continue;
- if (!is_fptr(fieldtype))
- return 0;
-
- if (code != RECORD_TYPE && code != UNION_TYPE)
- continue;
+ if (code == RECORD_TYPE || code == UNION_TYPE) {
+ if (!is_pure_ops_struct(fieldtype))
+ return 0;
+ }
- if (!is_pure_ops_struct(fieldtype))
+ if (!is_fptr(fieldtype))
return 0;
}
--
2.17.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] randstruct: fix a bug in is_pure_ops_struct()
2019-07-27 15:58 [PATCH] randstruct: fix a bug in is_pure_ops_struct() Joonwon Kang
@ 2019-07-30 17:11 ` Kees Cook
2019-07-31 16:25 ` Joonwon Kang
0 siblings, 1 reply; 3+ messages in thread
From: Kees Cook @ 2019-07-30 17:11 UTC (permalink / raw)
To: Joonwon Kang; +Cc: re.emese, kernel-hardening, linux-kernel, kernel-janitors
On Sun, Jul 28, 2019 at 12:58:41AM +0900, Joonwon Kang wrote:
> Before this, there were false negatives in the case where a struct
> contains other structs which contain only function pointers because
> of unreachable code in is_pure_ops_struct().
Ah, very true. Something like:
struct internal {
void (*callback)(void);
};
struct wrapper {
struct internal foo;
void (*other_callback)(void);
};
would have not been detected as is_pure_ops_struct()?
How did you notice this? (Are there cases of this in the kernel?)
> Signed-off-by: Joonwon Kang <kjw1627@gmail.com>
Applied; thanks!
-Kees
> ---
> scripts/gcc-plugins/randomize_layout_plugin.c | 11 +++++------
> 1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/scripts/gcc-plugins/randomize_layout_plugin.c b/scripts/gcc-plugins/randomize_layout_plugin.c
> index 6d5bbd31db7f..a123282a4fcd 100644
> --- a/scripts/gcc-plugins/randomize_layout_plugin.c
> +++ b/scripts/gcc-plugins/randomize_layout_plugin.c
> @@ -443,13 +443,12 @@ static int is_pure_ops_struct(const_tree node)
> if (node == fieldtype)
> continue;
>
> - if (!is_fptr(fieldtype))
> - return 0;
> -
> - if (code != RECORD_TYPE && code != UNION_TYPE)
> - continue;
> + if (code == RECORD_TYPE || code == UNION_TYPE) {
> + if (!is_pure_ops_struct(fieldtype))
> + return 0;
> + }
>
> - if (!is_pure_ops_struct(fieldtype))
> + if (!is_fptr(fieldtype))
> return 0;
> }
>
> --
> 2.17.1
>
--
Kees Cook
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] randstruct: fix a bug in is_pure_ops_struct()
2019-07-30 17:11 ` Kees Cook
@ 2019-07-31 16:25 ` Joonwon Kang
0 siblings, 0 replies; 3+ messages in thread
From: Joonwon Kang @ 2019-07-31 16:25 UTC (permalink / raw)
To: Kees Cook
Cc: re.emese, kernel-hardening, linux-kernel, kernel-janitors, jinb.park7
On Tue, Jul 30, 2019 at 10:11:19AM -0700, Kees Cook wrote:
> On Sun, Jul 28, 2019 at 12:58:41AM +0900, Joonwon Kang wrote:
> > Before this, there were false negatives in the case where a struct
> > contains other structs which contain only function pointers because
> > of unreachable code in is_pure_ops_struct().
>
> Ah, very true. Something like:
>
> struct internal {
> void (*callback)(void);
> };
>
> struct wrapper {
> struct internal foo;
> void (*other_callback)(void);
> };
>
> would have not been detected as is_pure_ops_struct()?
>
> How did you notice this? (Are there cases of this in the kernel?)
When I compiled kernel with allyesconfig, there seemed to be no such cases,
but I found the bug just by code review and test.
However, I would like to slightly modify this patch and add one more patch.
I will send the patch set soon.
>
> > Signed-off-by: Joonwon Kang <kjw1627@gmail.com>
>
> Applied; thanks!
>
> -Kees
>
> > ---
> > scripts/gcc-plugins/randomize_layout_plugin.c | 11 +++++------
> > 1 file changed, 5 insertions(+), 6 deletions(-)
> >
> > diff --git a/scripts/gcc-plugins/randomize_layout_plugin.c b/scripts/gcc-plugins/randomize_layout_plugin.c
> > index 6d5bbd31db7f..a123282a4fcd 100644
> > --- a/scripts/gcc-plugins/randomize_layout_plugin.c
> > +++ b/scripts/gcc-plugins/randomize_layout_plugin.c
> > @@ -443,13 +443,12 @@ static int is_pure_ops_struct(const_tree node)
> > if (node == fieldtype)
> > continue;
> >
> > - if (!is_fptr(fieldtype))
> > - return 0;
> > -
> > - if (code != RECORD_TYPE && code != UNION_TYPE)
> > - continue;
> > + if (code == RECORD_TYPE || code == UNION_TYPE) {
> > + if (!is_pure_ops_struct(fieldtype))
> > + return 0;
> > + }
> >
> > - if (!is_pure_ops_struct(fieldtype))
> > + if (!is_fptr(fieldtype))
> > return 0;
> > }
> >
> > --
> > 2.17.1
> >
>
> --
> Kees Cook
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-07-30 17:11 ` Kees Cook
2019-07-31 16:25 ` Joonwon Kang
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