On Fri, Aug 4, 2023, at 10:16, Herbert Xu wrote: > On Mon, Jul 24, 2023 at 03:53:01PM +0200, Arnd Bergmann wrote: >> From: Arnd Bergmann <arnd@xxxxxxxx> >> >> Some configurations with gcc-12 or gcc-13 produce a warning for the source >> and destination of a memcpy() in atmel_sha_hmac_compute_ipad_hash() potentially >> overlapping: >> >> In file included from include/linux/string.h:254, >> from drivers/crypto/atmel-sha.c:15: >> drivers/crypto/atmel-sha.c: In function 'atmel_sha_hmac_compute_ipad_hash': >> include/linux/fortify-string.h:57:33: error: '__builtin_memcpy' accessing 129 or more bytes at offsets 408 and 280 overlaps 1 or more bytes at offset 408 [-Werror=restrict] >> 57 | #define __underlying_memcpy __builtin_memcpy >> | ^ >> include/linux/fortify-string.h:648:9: note: in expansion of macro '__underlying_memcpy' >> 648 | __underlying_##op(p, q, __fortify_size); \ >> | ^~~~~~~~~~~~~ >> include/linux/fortify-string.h:693:26: note: in expansion of macro '__fortify_memcpy_chk' >> 693 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ >> | ^~~~~~~~~~~~~~~~~~~~ >> drivers/crypto/atmel-sha.c:1773:9: note: in expansion of macro 'memcpy' >> 1773 | memcpy(hmac->opad, hmac->ipad, bs); >> | ^~~~~~ >> >> The same thing happens in two more drivers that have the same logic: > > Please send me the configurations which triggers these warnings. > As these are false positives, I'd like to enable them only on the > configurations where they actually cause a problem. See https://pastebin.com/raw/ip3tfpJF for a config that triggers this on x86 with the chelsio and atmel drivers. The bcm driver is only available on arm64, so you won't hit that one here. I also see this with allmodconfig, as well as defconfig after enabling CONFIG_FORTIFY_SOURCE and the three crypto drivers. I see that commit df8fc4e934c12 ("kbuild: Enable -fstrict-flex-arrays=3") turned on the strict flex-array behavior that triggers the warning, so this did not show up until linux-6.5-rc1. In linux-next, I see no other code hit this warning after all my other patches for it got merged, regardless strict flex arrays. At the moment, -Wrestrict is completely disabled in all builds, so you have to add a patch to enable it in the build system, this is what I use locally to enable it at the W=1 level, though you can probably just replace the cc-disable-warning line with a -Wrestrict line. Arnd --- a/scripts/Makefile.extrawarn +++ b/scripts/Makefile.extrawarn @@ -49,9 +49,6 @@ KBUILD_CFLAGS += -Wno-pointer-sign # globally built with -Wcast-function-type. KBUILD_CFLAGS += $(call cc-option, -Wcast-function-type) -# Another good warning that we'll want to enable eventually -KBUILD_CFLAGS += $(call cc-disable-warning, restrict) - # The allocators already balk at large sizes, so silence the compiler # warnings for bounds checks involving those possible values. While # -Wno-alloc-size-larger-than would normally be used here, earlier versions @@ -93,6 +90,7 @@ export KBUILD_EXTRA_WARN ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),) KBUILD_CFLAGS += -Wextra -Wunused -Wno-unused-parameter +KBUILD_CFLAGS += $(call cc-option, -Wrestrict) KBUILD_CFLAGS += -Wmissing-format-attribute KBUILD_CFLAGS += -Wold-style-definition KBUILD_CFLAGS += -Wmissing-include-dirs @@ -105,6 +103,7 @@ else # Some diagnostics enabled by default are noisy. # Suppress them by using -Wno... except for W=1. +KBUILD_CFLAGS += $(call cc-disable-warning, restrict) KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned) ifdef CONFIG_CC_IS_CLANG
