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) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/lib/Makefile b/lib/Makefile
index 3b08673e8881a42c9abcd67269455f69fbd9ceb0..c4563e7c47ba8894638e2ba1d834d336de7844a8 100644 (file)
--- 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 e4162f59a81ccacda275cd218193fb2ad34d71d3..c8e905bfb627ea919ef94be2bc9987402143cca6 100644 (file)
--- a/lib/ubsan.c
+++ b/lib/ubsan.c
@@ -17,6 +17,7 @@
 #include <linux/kernel.h>
 #include <linux/types.h>
 #include <linux/sched.h>
+#include <linux/uaccess.h>
 
 #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,