From d08965a27e84ca090b504844d50c24fc98587b11 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 3 Apr 2019 09:40:16 +0200 Subject: x86/uaccess, ubsan: Fix UBSAN vs. SMAP UBSAN can insert extra code in random locations; including AC=1 sections. Typically this code is not safe and needs wrapping. So far, only __ubsan_handle_type_mismatch* have been observed in AC=1 sections and therefore only those are annotated. Signed-off-by: Peter Zijlstra (Intel) Cc: Borislav Petkov Cc: Dmitry Vyukov Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Ingo Molnar --- lib/Makefile | 1 + lib/ubsan.c | 4 ++++ 2 files changed, 5 insertions(+) (limited to 'lib') diff --git a/lib/Makefile b/lib/Makefile index 3b08673e8881..c4563e7c47ba 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -268,6 +268,7 @@ obj-$(CONFIG_UCS2_STRING) += ucs2_string.o obj-$(CONFIG_UBSAN) += ubsan.o UBSAN_SANITIZE_ubsan.o := n +CFLAGS_ubsan.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) obj-$(CONFIG_SBITMAP) += sbitmap.o diff --git a/lib/ubsan.c b/lib/ubsan.c index e4162f59a81c..c8e905bfb627 100644 --- a/lib/ubsan.c +++ b/lib/ubsan.c @@ -17,6 +17,7 @@ #include #include #include +#include #include "ubsan.h" @@ -313,6 +314,7 @@ static void handle_object_size_mismatch(struct type_mismatch_data_common *data, static void ubsan_type_mismatch_common(struct type_mismatch_data_common *data, unsigned long ptr) { + unsigned long flags = user_access_save(); if (!ptr) handle_null_ptr_deref(data); @@ -320,6 +322,8 @@ static void ubsan_type_mismatch_common(struct type_mismatch_data_common *data, handle_misaligned_access(data, ptr); else handle_object_size_mismatch(data, ptr); + + user_access_restore(flags); } void __ubsan_handle_type_mismatch(struct type_mismatch_data *data, -- cgit From 29da93fea3ea39ab9b12270cc6be1b70ef201c9e Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 24 Apr 2019 09:19:25 +0200 Subject: mm/uaccess: Use 'unsigned long' to placate UBSAN warnings on older GCC versions Randy reported objtool triggered on his (GCC-7.4) build: lib/strncpy_from_user.o: warning: objtool: strncpy_from_user()+0x315: call to __ubsan_handle_add_overflow() with UACCESS enabled lib/strnlen_user.o: warning: objtool: strnlen_user()+0x337: call to __ubsan_handle_sub_overflow() with UACCESS enabled This is due to UBSAN generating signed-overflow-UB warnings where it should not. Prior to GCC-8 UBSAN ignored -fwrapv (which the kernel uses through -fno-strict-overflow). Make the functions use 'unsigned long' throughout. Reported-by: Randy Dunlap Signed-off-by: Peter Zijlstra (Intel) Acked-by: Randy Dunlap # build-tested Acked-by: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: luto@kernel.org Link: http://lkml.kernel.org/r/20190424072208.754094071@infradead.org Signed-off-by: Ingo Molnar --- lib/strncpy_from_user.c | 5 +++-- lib/strnlen_user.c | 4 ++-- 2 files changed, 5 insertions(+), 4 deletions(-) (limited to 'lib') diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c index 58eacd41526c..023ba9f3b99f 100644 --- a/lib/strncpy_from_user.c +++ b/lib/strncpy_from_user.c @@ -23,10 +23,11 @@ * hit it), 'max' is the address space maximum (and we return * -EFAULT if we hit it). */ -static inline long do_strncpy_from_user(char *dst, const char __user *src, long count, unsigned long max) +static inline long do_strncpy_from_user(char *dst, const char __user *src, + unsigned long count, unsigned long max) { const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; - long res = 0; + unsigned long res = 0; /* * Truncate 'max' to the user-specified limit, so that diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c index 1c1a1b0e38a5..7f2db3fe311f 100644 --- a/lib/strnlen_user.c +++ b/lib/strnlen_user.c @@ -28,7 +28,7 @@ static inline long do_strnlen_user(const char __user *src, unsigned long count, unsigned long max) { const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; - long align, res = 0; + unsigned long align, res = 0; unsigned long c; /* @@ -42,7 +42,7 @@ static inline long do_strnlen_user(const char __user *src, unsigned long count, * Do everything aligned. But that means that we * need to also expand the maximum.. */ - align = (sizeof(long) - 1) & (unsigned long)src; + align = (sizeof(unsigned long) - 1) & (unsigned long)src; src -= align; max += align; -- cgit