On Tue, Jul 18, 2017 at 7:15 PM, Andrey Ryabinin <[email protected]> wrote: > strscpy() performs the word-at-a-time optimistic reads. So it may > may access the memory past the end of the object, which is perfectly fine > since strscpy() doesn't use that (past-the-end) data and makes sure the > optimistic read won't cross a page boundary. > > But KASAN doesn't know anything about that so it will complain. > Let's just fallback to the byte-at-a-time reads under CONFIG_KASAN=y > to avoid false-positives.
Acked-by: Dmitry Vyukov <[email protected]> > Reported-by: Dave Jones <[email protected]> > Signed-off-by: Andrey Ryabinin <[email protected]> > --- > lib/string.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/lib/string.c b/lib/string.c > index ebbb99c775bd..8b93d2519d5a 100644 > --- a/lib/string.c > +++ b/lib/string.c > @@ -199,6 +199,13 @@ ssize_t strscpy(char *dest, const char *src, size_t > count) > max = 0; > #endif > > + /* > + * KASAN won't be happy about word-at-a-time > + * optimistic reads, so let's avoid them. > + */ > + if (IS_ENABLED(CONFIG_KASAN)) > + max = 0; > + > while (max >= sizeof(unsigned long)) { > unsigned long c, data; > > -- > 2.13.0 >
