* [PATCH] comedi: drivers: ni_routes: Use strcmp() instead of memcmp()
@ 2022-02-15 17:10 Kees Cook
2022-02-16 15:03 ` Ian Abbott
0 siblings, 1 reply; 3+ messages in thread
From: Kees Cook @ 2022-02-15 17:10 UTC (permalink / raw)
To: Ian Abbott
Cc: Kees Cook, H Hartley Sweeten, Spencer E . Olson,
Greg Kroah-Hartman, Masahiro Yamada, Lee Jones,
kernel test robot, Nathan Chancellor, Nick Desaulniers,
linux-kernel, llvm, linux-hardening
The family and device comparisons were using memcmp(), but this could
lead to Out-of-bounds reads when the length was larger than the
buffers being compared. Since these appear to always be NUL-terminated
strings, just use strcmp() instead.
This was found with Clang under LTO:
[ 92.405851][ T1] kernel BUG at lib/string_helpers.c:980!
...
[ 92.409141][ T1] RIP: 0010:fortify_panic (fbdev.c:?)
...
[ 92.410056][ T1] ni_assign_device_routes (fbdev.c:?)
[ 92.410056][ T1] ? unittest_enter (fbdev.c:?)
[ 92.410056][ T1] ni_routes_unittest (ni_routes_test.c:?)
[ 92.410056][ T1] ? unittest_enter (fbdev.c:?)
[ 92.410056][ T1] __initstub__kmod_ni_routes_test__505_604_ni_routes_unittest6 (fbdev.c:?)
[ 92.410056][ T1] do_one_initcall (fbdev.c:?)
Cc: Ian Abbott <abbotti@mev.co.uk>
Cc: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Spencer E. Olson <olsonse@umich.edu>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Lee Jones <lee.jones@linaro.org>
Reported-by: kernel test robot <oliver.sang@intel.com>
Link: https://lore.kernel.org/lkml/20220210072821.GD4074@xsang-OptiPlex-9020
Fixes: 4bb90c87abbe ("staging: comedi: add interface to ni routing table information")
Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/comedi/drivers/ni_routes.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/drivers/comedi/drivers/ni_routes.c b/drivers/comedi/drivers/ni_routes.c
index f24eeb464eba..295a3a9ee0c9 100644
--- a/drivers/comedi/drivers/ni_routes.c
+++ b/drivers/comedi/drivers/ni_routes.c
@@ -56,8 +56,7 @@ static const u8 *ni_find_route_values(const char *device_family)
int i;
for (i = 0; ni_all_route_values[i]; ++i) {
- if (memcmp(ni_all_route_values[i]->family, device_family,
- strnlen(device_family, 30)) == 0) {
+ if (!strcmp(ni_all_route_values[i]->family, device_family)) {
rv = &ni_all_route_values[i]->register_values[0][0];
break;
}
@@ -75,8 +74,7 @@ ni_find_valid_routes(const char *board_name)
int i;
for (i = 0; ni_device_routes_list[i]; ++i) {
- if (memcmp(ni_device_routes_list[i]->device, board_name,
- strnlen(board_name, 30)) == 0) {
+ if (!strcmp(ni_device_routes_list[i]->device, board_name)) {
dr = ni_device_routes_list[i];
break;
}
--
2.30.2
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] comedi: drivers: ni_routes: Use strcmp() instead of memcmp()
2022-02-15 17:10 [PATCH] comedi: drivers: ni_routes: Use strcmp() instead of memcmp() Kees Cook
@ 2022-02-16 15:03 ` Ian Abbott
2022-02-16 16:15 ` Spencer Olson
0 siblings, 1 reply; 3+ messages in thread
From: Ian Abbott @ 2022-02-16 15:03 UTC (permalink / raw)
To: Kees Cook
Cc: H Hartley Sweeten, Spencer E . Olson, Greg Kroah-Hartman,
Masahiro Yamada, Lee Jones, kernel test robot, Nathan Chancellor,
Nick Desaulniers, linux-kernel, llvm, linux-hardening
On 15/02/2022 17:10, Kees Cook wrote:
> The family and device comparisons were using memcmp(), but this could
> lead to Out-of-bounds reads when the length was larger than the
> buffers being compared. Since these appear to always be NUL-terminated
> strings, just use strcmp() instead.
>
> This was found with Clang under LTO:
>
> [ 92.405851][ T1] kernel BUG at lib/string_helpers.c:980!
> ...
> [ 92.409141][ T1] RIP: 0010:fortify_panic (fbdev.c:?)
> ...
> [ 92.410056][ T1] ni_assign_device_routes (fbdev.c:?)
> [ 92.410056][ T1] ? unittest_enter (fbdev.c:?)
> [ 92.410056][ T1] ni_routes_unittest (ni_routes_test.c:?)
> [ 92.410056][ T1] ? unittest_enter (fbdev.c:?)
> [ 92.410056][ T1] __initstub__kmod_ni_routes_test__505_604_ni_routes_unittest6 (fbdev.c:?)
> [ 92.410056][ T1] do_one_initcall (fbdev.c:?)
>
> Cc: Ian Abbott <abbotti@mev.co.uk>
> Cc: H Hartley Sweeten <hsweeten@visionengravers.com>
> Cc: Spencer E. Olson <olsonse@umich.edu>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Cc: Lee Jones <lee.jones@linaro.org>
> Reported-by: kernel test robot <oliver.sang@intel.com>
> Link: https://lore.kernel.org/lkml/20220210072821.GD4074@xsang-OptiPlex-9020
> Fixes: 4bb90c87abbe ("staging: comedi: add interface to ni routing table information")
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> drivers/comedi/drivers/ni_routes.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/comedi/drivers/ni_routes.c b/drivers/comedi/drivers/ni_routes.c
> index f24eeb464eba..295a3a9ee0c9 100644
> --- a/drivers/comedi/drivers/ni_routes.c
> +++ b/drivers/comedi/drivers/ni_routes.c
> @@ -56,8 +56,7 @@ static const u8 *ni_find_route_values(const char *device_family)
> int i;
>
> for (i = 0; ni_all_route_values[i]; ++i) {
> - if (memcmp(ni_all_route_values[i]->family, device_family,
> - strnlen(device_family, 30)) == 0) {
> + if (!strcmp(ni_all_route_values[i]->family, device_family)) {
> rv = &ni_all_route_values[i]->register_values[0][0];
> break;
> }
> @@ -75,8 +74,7 @@ ni_find_valid_routes(const char *board_name)
> int i;
>
> for (i = 0; ni_device_routes_list[i]; ++i) {
> - if (memcmp(ni_device_routes_list[i]->device, board_name,
> - strnlen(board_name, 30)) == 0) {
> + if (!strcmp(ni_device_routes_list[i]->device, board_name)) {
> dr = ni_device_routes_list[i];
> break;
> }
Looks good, thanks! I'm not sure why the tests used memcmp() like that.
Indeed, all the strings are statically allocated and null-terminated.
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
--
-=( Ian Abbott <abbotti@mev.co.uk> || MEV Ltd. is a company )=-
-=( registered in England & Wales. Regd. number: 02862268. )=-
-=( Regd. addr.: S11 & 12 Building 67, Europa Business Park, )=-
-=( Bird Hall Lane, STOCKPORT, SK3 0XA, UK. || www.mev.co.uk )=-
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] comedi: drivers: ni_routes: Use strcmp() instead of memcmp()
2022-02-16 15:03 ` Ian Abbott
@ 2022-02-16 16:15 ` Spencer Olson
0 siblings, 0 replies; 3+ messages in thread
From: Spencer Olson @ 2022-02-16 16:15 UTC (permalink / raw)
To: Ian Abbott
Cc: Kees Cook, H Hartley Sweeten, Greg Kroah-Hartman,
Masahiro Yamada, Lee Jones, kernel test robot, Nathan Chancellor,
Nick Desaulniers, linux-kernel, llvm, linux-hardening
On Wed, Feb 16, 2022 at 8:03 AM Ian Abbott <abbotti@mev.co.uk> wrote:
>
> On 15/02/2022 17:10, Kees Cook wrote:
> > The family and device comparisons were using memcmp(), but this could
> > lead to Out-of-bounds reads when the length was larger than the
> > buffers being compared. Since these appear to always be NUL-terminated
> > strings, just use strcmp() instead.
> >
> > This was found with Clang under LTO:
> >
> > [ 92.405851][ T1] kernel BUG at lib/string_helpers.c:980!
> > ...
> > [ 92.409141][ T1] RIP: 0010:fortify_panic (fbdev.c:?)
> > ...
> > [ 92.410056][ T1] ni_assign_device_routes (fbdev.c:?)
> > [ 92.410056][ T1] ? unittest_enter (fbdev.c:?)
> > [ 92.410056][ T1] ni_routes_unittest (ni_routes_test.c:?)
> > [ 92.410056][ T1] ? unittest_enter (fbdev.c:?)
> > [ 92.410056][ T1] __initstub__kmod_ni_routes_test__505_604_ni_routes_unittest6 (fbdev.c:?)
> > [ 92.410056][ T1] do_one_initcall (fbdev.c:?)
> >
> > Cc: Ian Abbott <abbotti@mev.co.uk>
> > Cc: H Hartley Sweeten <hsweeten@visionengravers.com>
> > Cc: Spencer E. Olson <olsonse@umich.edu>
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Cc: Masahiro Yamada <masahiroy@kernel.org>
> > Cc: Lee Jones <lee.jones@linaro.org>
> > Reported-by: kernel test robot <oliver.sang@intel.com>
> > Link: https://lore.kernel.org/lkml/20220210072821.GD4074@xsang-OptiPlex-9020
> > Fixes: 4bb90c87abbe ("staging: comedi: add interface to ni routing table information")
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> > drivers/comedi/drivers/ni_routes.c | 6 ++----
> > 1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/comedi/drivers/ni_routes.c b/drivers/comedi/drivers/ni_routes.c
> > index f24eeb464eba..295a3a9ee0c9 100644
> > --- a/drivers/comedi/drivers/ni_routes.c
> > +++ b/drivers/comedi/drivers/ni_routes.c
> > @@ -56,8 +56,7 @@ static const u8 *ni_find_route_values(const char *device_family)
> > int i;
> >
> > for (i = 0; ni_all_route_values[i]; ++i) {
> > - if (memcmp(ni_all_route_values[i]->family, device_family,
> > - strnlen(device_family, 30)) == 0) {
> > + if (!strcmp(ni_all_route_values[i]->family, device_family)) {
> > rv = &ni_all_route_values[i]->register_values[0][0];
> > break;
> > }
> > @@ -75,8 +74,7 @@ ni_find_valid_routes(const char *board_name)
> > int i;
> >
> > for (i = 0; ni_device_routes_list[i]; ++i) {
> > - if (memcmp(ni_device_routes_list[i]->device, board_name,
> > - strnlen(board_name, 30)) == 0) {
> > + if (!strcmp(ni_device_routes_list[i]->device, board_name)) {
> > dr = ni_device_routes_list[i];
> > break;
> > }
>
> Looks good, thanks! I'm not sure why the tests used memcmp() like that.
> Indeed, all the strings are statically allocated and null-terminated.
>
> Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
>
> --
> -=( Ian Abbott <abbotti@mev.co.uk> || MEV Ltd. is a company )=-
> -=( registered in England & Wales. Regd. number: 02862268. )=-
> -=( Regd. addr.: S11 & 12 Building 67, Europa Business Park, )=-
> -=( Bird Hall Lane, STOCKPORT, SK3 0XA, UK. || www.mev.co.uk )=-
I was probably just being paranoid when I wrote that.
Spencer
^ permalink raw reply [flat|nested] 3+ messages in thread
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