Messages in this thread | | | Date | Wed, 16 Feb 2022 15:03:45 +0000 | Subject | Re: [PATCH] comedi: drivers: ni_routes: Use strcmp() instead of memcmp() | From | Ian Abbott <> |
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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>
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