| Message ID | 20230530083911.1104336-1-glider@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] string: use __builtin_memcpy() in strlcpy/strlcat | expand |
On Tue, May 30, 2023 at 10:39 AM Alexander Potapenko <glider@google.com> wrote: > > lib/string.c is built with -ffreestanding, which prevents the compiler > from replacing certain functions with calls to their library versions. > > On the other hand, this also prevents Clang and GCC from instrumenting > calls to memcpy() when building with KASAN, KCSAN or KMSAN: > - KASAN normally replaces memcpy() with __asan_memcpy() with the > additional cc-param,asan-kernel-mem-intrinsic-prefix=1; > - KCSAN and KMSAN replace memcpy() with __tsan_memcpy() and > __msan_memcpy() by default. > > To let the tools catch memory accesses from strlcpy/strlcat, replace > the calls to memcpy() with __builtin_memcpy(), which KASAN, KCSAN and > KMSAN are able to replace even in -ffreestanding mode. > > This preserves the behavior in normal builds (__builtin_memcpy() ends up > being replaced with memcpy()), and does not introduce new instrumentation > in unwanted places, as strlcpy/strlcat are already instrumented. > > Suggested-by: Marco Elver <elver@google.com> > Signed-off-by: Alexander Potapenko <glider@google.com> > Link: https://lore.kernel.org/all/20230224085942.1791837-1-elver@google.com/ Sorry, missed a "Reviewed-by: Marco Elver <elver@google.com>" from the previous thread: https://lore.kernel.org/lkml/CAG_fn=UzQ-jnQrxzvLE6EV37zSVCOGPmsVTxyfp1wXzBir4vAg@mail.gmail.com/T/ > Acked-by: Kees Cook <keescook@chromium.org>
On Tue, 30 May 2023 10:39:11 +0200, Alexander Potapenko wrote: > lib/string.c is built with -ffreestanding, which prevents the compiler > from replacing certain functions with calls to their library versions. > > On the other hand, this also prevents Clang and GCC from instrumenting > calls to memcpy() when building with KASAN, KCSAN or KMSAN: > - KASAN normally replaces memcpy() with __asan_memcpy() with the > additional cc-param,asan-kernel-mem-intrinsic-prefix=1; > - KCSAN and KMSAN replace memcpy() with __tsan_memcpy() and > __msan_memcpy() by default. > > [...] Applied to for-next/hardening, thanks! [1/1] string: use __builtin_memcpy() in strlcpy/strlcat https://git.kernel.org/kees/c/cfe93c8c9a7a
On Wed, May 31, 2023 at 1:10 AM Kees Cook <keescook@chromium.org> wrote: > > On Tue, 30 May 2023 10:39:11 +0200, Alexander Potapenko wrote: > > lib/string.c is built with -ffreestanding, which prevents the compiler > > from replacing certain functions with calls to their library versions. > > > > On the other hand, this also prevents Clang and GCC from instrumenting > > calls to memcpy() when building with KASAN, KCSAN or KMSAN: > > - KASAN normally replaces memcpy() with __asan_memcpy() with the > > additional cc-param,asan-kernel-mem-intrinsic-prefix=1; > > - KCSAN and KMSAN replace memcpy() with __tsan_memcpy() and > > __msan_memcpy() by default. > > > > [...] > > Applied to for-next/hardening, thanks! > > [1/1] string: use __builtin_memcpy() in strlcpy/strlcat > https://git.kernel.org/kees/c/cfe93c8c9a7a Note that Andrew also picked it to mm-unstable
diff --git a/lib/string.c b/lib/string.c index 3d55ef8901068..be26623953d2e 100644 --- a/lib/string.c +++ b/lib/string.c @@ -110,7 +110,7 @@ size_t strlcpy(char *dest, const char *src, size_t size) if (size) { size_t len = (ret >= size) ? size - 1 : ret; - memcpy(dest, src, len); + __builtin_memcpy(dest, src, len); dest[len] = '\0'; } return ret; @@ -260,7 +260,7 @@ size_t strlcat(char *dest, const char *src, size_t count) count -= dsize; if (len >= count) len = count-1; - memcpy(dest, src, len); + __builtin_memcpy(dest, src, len); dest[len] = 0; return res; }