From 8185be3307232d88ddd1b6468f4ddec54a993f54 Mon Sep 17 00:00:00 2001 From: Alex Richardson Date: Mon, 2 Aug 2021 09:51:34 +0100 Subject: [PATCH] libc: Disable ASAN for certain string functions They deliberately read out-of-bounds values to avoid byte-by-byte loads and check multiple bytes at once. While this will work on x86, it is flagged as an out-of-bounds read with ASAN, so we have to disable instrumentation here. This also causes bounds errors for CHERI, so in CheriBSD we use implementations that avoid OOB reads. Differential Revision: https://reviews.freebsd.org/D31045 --- lib/libc/string/Makefile.inc | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/lib/libc/string/Makefile.inc b/lib/libc/string/Makefile.inc index 6945155812af..1df3d40e329f 100644 --- a/lib/libc/string/Makefile.inc +++ b/lib/libc/string/Makefile.inc @@ -29,6 +29,15 @@ MISRCS+=bcmp.c bcopy.c bzero.c explicit_bzero.c \ SYM_MAPS+= ${LIBC_SRCTOP}/string/Symbol.map +.if ${MK_ASAN} != "no" +# These source files deliberately read out of bounds since they assume that +# out-of-bounds memory accesses that don't cross pages are always legal. +# Note: While this is fine on x86, it does break when running with CHERI. +CFLAGS.strlen.c+= -fno-sanitize=address +CFLAGS.strchrnul.c+= -fno-sanitize=address +CFLAGS.memchr.c+= -fno-sanitize=address +.endif + # machine-dependent string sources .sinclude "${LIBC_SRCTOP}/${LIBC_ARCH}/string/Makefile.inc"