[v3,2/2] UBSAN: run-time undefined behavior sanity checker
diff mbox

Message ID 1448899183-8677-3-git-send-email-aryabinin@virtuozzo.com
State New
Headers show

Commit Message

Andrey Ryabinin Nov. 30, 2015, 3:59 p.m. UTC
UBSAN uses compile-time instrumentation to catch undefined behavior (UB).
Compiler inserts code that perform certain kinds of checks before
operations that could cause UB. If check fails (i.e. UB detected)
__ubsan_handle_* function called to print error message.

So the most of the work is done by compiler. This patch just
implements ubsan handlers printing errors.

GCC has this capability since 4.9.x [1] (see -fsanitize=undefined
option and its suboptions).
However GCC 5.x has more checkers implemented [2].
Article [3] has a bit more details about UBSAN in the GCC.

[1] - https://gcc.gnu.org/onlinedocs/gcc-4.9.0/gcc/Debugging-Options.html
[2] - https://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html
[3] - http://developerblog.redhat.com/2014/10/16/gcc-undefined-behavior-sanitizer-ubsan/

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
---
 Documentation/ubsan.txt               |  84 +++++++
 Makefile                              |   3 +-
 arch/x86/Kconfig                      |   1 +
 arch/x86/boot/Makefile                |   1 +
 arch/x86/boot/compressed/Makefile     |   1 +
 arch/x86/entry/vdso/Makefile          |   1 +
 arch/x86/realmode/rm/Makefile         |   1 +
 drivers/firmware/efi/libstub/Makefile |   1 +
 include/linux/sched.h                 |   3 +
 lib/Kconfig.debug                     |   1 +
 lib/Kconfig.ubsan                     |  29 +++
 lib/Makefile                          |   3 +
 lib/ubsan.c                           | 452 ++++++++++++++++++++++++++++++++++
 lib/ubsan.h                           |  84 +++++++
 mm/kasan/Makefile                     |   1 +
 scripts/Makefile.lib                  |   6 +
 scripts/Makefile.ubsan                |  18 ++
 17 files changed, 689 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/ubsan.txt
 create mode 100644 lib/Kconfig.ubsan
 create mode 100644 lib/ubsan.c
 create mode 100644 lib/ubsan.h
 create mode 100644 scripts/Makefile.ubsan

Comments

kbuild test robot Nov. 30, 2015, 4:47 p.m. UTC | #1
Hi Andrey,

[auto build test ERROR on: v4.4-rc3]
[cannot apply to: tip/x86/core kbuild/for-next next-20151127]

url:    https://github.com/0day-ci/linux/commits/Andrey-Ryabinin/kernel-printk-specify-alignment-for-struct-printk_log/20151201-000229
config: i386-allmodconfig (attached as .config)
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All error/warnings (new ones prefixed by >>):

   lib/ubsan.c: In function 'val_to_string':
>> lib/ubsan.c:127:15: warning: right shift count >= width of type [-Wshift-count-overflow]
        (u32)(val >> 96),
                  ^
   lib/ubsan.c:128:15: warning: right shift count >= width of type [-Wshift-count-overflow]
        (u32)(val >> 64),
                  ^
--
   In file included from include/linux/linkage.h:4:0,
                    from include/linux/fs.h:4,
                    from include/linux/debugfs.h:18,
                    from net/mac80211/debugfs.c:11:
   net/mac80211/debugfs.c: In function 'hwflags_read':
>> include/linux/compiler.h:484:38: error: call to '__compiletime_assert_150' declared with attribute error: BUILD_BUG_ON failed: hw_flag_names[NUM_IEEE80211_HW_FLAGS] != (void *)0x1
     _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
                                         ^
   include/linux/compiler.h:467:4: note: in definition of macro '__compiletime_assert'
       prefix ## suffix();    \
       ^
   include/linux/compiler.h:484:2: note: in expansion of macro '_compiletime_assert'
     _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
     ^
   include/linux/bug.h:50:37: note: in expansion of macro 'compiletime_assert'
    #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
                                        ^
   include/linux/bug.h:74:2: note: in expansion of macro 'BUILD_BUG_ON_MSG'
     BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
     ^
>> net/mac80211/debugfs.c:150:2: note: in expansion of macro 'BUILD_BUG_ON'
     BUILD_BUG_ON(hw_flag_names[NUM_IEEE80211_HW_FLAGS] != (void *)0x1);
     ^

vim +127 lib/ubsan.c

   111	
   112		if (type_bit_width(type) == 64)
   113			return *(u64 *)val;
   114	
   115		return *(u_max *)val;
   116	}
   117	
   118	static void val_to_string(char *str, size_t size, struct type_descriptor *type,
   119		unsigned long value)
   120	{
   121		u_max val = get_unsigned_val(type, value);
   122	
   123		if (type_is_int(type)) {
   124			if (IS_ENABLED(CONFIG_ARCH_SUPPORTS_INT128)
   125				&& type_bit_width(type) == 128)
   126				scnprintf(str, size, "0x%08x%08x%08x%08x",
 > 127					(u32)(val >> 96),
   128					(u32)(val >> 64),
   129					(u32)(val >> 32),
   130					(u32)(val));
   131			else if (type_is_signed(type))
   132				scnprintf(str, size, "%lld",
   133					(s64)get_signed_val(type, value));
   134			else
   135				scnprintf(str, size, "%llu",

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
kbuild test robot Nov. 30, 2015, 5:23 p.m. UTC | #2
Hi Andrey,

[auto build test ERROR on: v4.4-rc3]
[cannot apply to: tip/x86/core kbuild/for-next next-20151127]

url:    https://github.com/0day-ci/linux/commits/Andrey-Ryabinin/kernel-printk-specify-alignment-for-struct-printk_log/20151201-000229
config: i386-allyesconfig (attached as .config)
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

   net/mac80211/debugfs.c: In function 'hwflags_read':
>> net/mac80211/debugfs.c:150:240: error: call to '__compiletime_assert_150' declared with attribute error: BUILD_BUG_ON failed: hw_flag_names[NUM_IEEE80211_HW_FLAGS] != (void *)0x1

vim +/__compiletime_assert_150 +150 net/mac80211/debugfs.c

279daf64 Ben Greear               2011-03-23  134  static ssize_t hwflags_read(struct file *file, char __user *user_buf,
279daf64 Ben Greear               2011-03-23  135  			    size_t count, loff_t *ppos)
279daf64 Ben Greear               2011-03-23  136  {
279daf64 Ben Greear               2011-03-23  137  	struct ieee80211_local *local = file->private_data;
30686bf7 Johannes Berg            2015-06-02  138  	size_t bufsz = 30 * NUM_IEEE80211_HW_FLAGS;
30686bf7 Johannes Berg            2015-06-02  139  	char *buf = kzalloc(bufsz, GFP_KERNEL);
30686bf7 Johannes Berg            2015-06-02  140  	char *pos = buf, *end = buf + bufsz - 1;
279daf64 Ben Greear               2011-03-23  141  	ssize_t rv;
30686bf7 Johannes Berg            2015-06-02  142  	int i;
279daf64 Ben Greear               2011-03-23  143  
d15b8459 Joe Perches              2011-08-29  144  	if (!buf)
30686bf7 Johannes Berg            2015-06-02  145  		return -ENOMEM;
30686bf7 Johannes Berg            2015-06-02  146  
30686bf7 Johannes Berg            2015-06-02  147  	/* fail compilation if somebody adds or removes
30686bf7 Johannes Berg            2015-06-02  148  	 * a flag without updating the name array above
30686bf7 Johannes Berg            2015-06-02  149  	 */
30686bf7 Johannes Berg            2015-06-02 @150  	BUILD_BUG_ON(hw_flag_names[NUM_IEEE80211_HW_FLAGS] != (void *)0x1);
30686bf7 Johannes Berg            2015-06-02  151  
30686bf7 Johannes Berg            2015-06-02  152  	for (i = 0; i < NUM_IEEE80211_HW_FLAGS; i++) {
30686bf7 Johannes Berg            2015-06-02  153  		if (test_bit(i, local->hw.flags))
4633dfc3 Mohammed Shafi Shajakhan 2015-10-08  154  			pos += scnprintf(pos, end - pos, "%s\n",
30686bf7 Johannes Berg            2015-06-02  155  					 hw_flag_names[i]);
30686bf7 Johannes Berg            2015-06-02  156  	}
279daf64 Ben Greear               2011-03-23  157  
279daf64 Ben Greear               2011-03-23  158  	rv = simple_read_from_buffer(user_buf, count, ppos, buf, strlen(buf));

:::::: The code at line 150 was first introduced by commit
:::::: 30686bf7f5b3c30831761e188a6e3cb33580fa48 mac80211: convert HW flags to unsigned long bitmap

:::::: TO: Johannes Berg <johannes.berg@intel.com>
:::::: CC: Johannes Berg <johannes.berg@intel.com>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
Sasha Levin Nov. 30, 2015, 6:50 p.m. UTC | #3
On 11/30/2015 10:59 AM, Andrey Ryabinin wrote:
> +void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data,
> +					unsigned long lhs, unsigned long rhs)
> +{
> +	unsigned long flags;
> +	struct type_descriptor *rhs_type = data->rhs_type;
> +	struct type_descriptor *lhs_type = data->lhs_type;
> +	char rhs_str[VALUE_LENGTH];
> +	char lhs_str[VALUE_LENGTH];
> +
> +	if (suppress_report(&data->location))
> +		return;
> +
> +	ubsan_prologue(&data->location, &flags);
> +
> +	val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs);
> +	val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs);
> +
> +	if (val_is_negative(rhs_type, rhs))
> +		pr_err("shift exponent %s is negative\n", rhs_str);
> +
> +	else if (get_unsigned_val(rhs_type, rhs) >=
> +		type_bit_width(lhs_type))
> +		pr_err("shift exponent %s is to large for %u-bit type %s\n",
					     too

Otherwise looks great, I'm running fuzzing with it now.


Thanks,
Sasha
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Patch
diff mbox

diff --git a/Documentation/ubsan.txt b/Documentation/ubsan.txt
new file mode 100644
index 0000000..f58215e
--- /dev/null
+++ b/Documentation/ubsan.txt
@@ -0,0 +1,84 @@ 
+Undefined Behavior Sanitizer - UBSAN
+
+Overview
+--------
+
+UBSAN is a runtime undefined behaviour checker.
+
+UBSAN uses compile-time instrumentation to catch undefined behavior (UB).
+Compiler inserts code that perform certain kinds of checks before operations
+that may cause UB. If check fails (i.e. UB detected) __ubsan_handle_*
+function called to print error message.
+
+GCC has that feature since 4.9.x [1] (see -fsanitize=undefined option and
+its suboptions). GCC 5.x has more checkers implemented [2].
+
+Report example
+---------------
+
+	 ================================================================================
+	 UBSAN: Undefined behaviour in ../include/linux/bitops.h:110:33
+	 shift exponent 32 is to large for 32-bit type 'unsigned int'
+	 CPU: 0 PID: 0 Comm: swapper Not tainted 4.4.0-rc1+ #26
+	  0000000000000000 ffffffff82403cc8 ffffffff815e6cd6 0000000000000001
+	  ffffffff82403cf8 ffffffff82403ce0 ffffffff8163a5ed 0000000000000020
+	  ffffffff82403d78 ffffffff8163ac2b ffffffff815f0001 0000000000000002
+	 Call Trace:
+	  [<ffffffff815e6cd6>] dump_stack+0x45/0x5f
+	  [<ffffffff8163a5ed>] ubsan_epilogue+0xd/0x40
+	  [<ffffffff8163ac2b>] __ubsan_handle_shift_out_of_bounds+0xeb/0x130
+	  [<ffffffff815f0001>] ? radix_tree_gang_lookup_slot+0x51/0x150
+	  [<ffffffff8173c586>] _mix_pool_bytes+0x1e6/0x480
+	  [<ffffffff83105653>] ? dmi_walk_early+0x48/0x5c
+	  [<ffffffff8173c881>] add_device_randomness+0x61/0x130
+	  [<ffffffff83105b35>] ? dmi_save_one_device+0xaa/0xaa
+	  [<ffffffff83105653>] dmi_walk_early+0x48/0x5c
+	  [<ffffffff831066ae>] dmi_scan_machine+0x278/0x4b4
+	  [<ffffffff8111d58a>] ? vprintk_default+0x1a/0x20
+	  [<ffffffff830ad120>] ? early_idt_handler_array+0x120/0x120
+	  [<ffffffff830b2240>] setup_arch+0x405/0xc2c
+	  [<ffffffff830ad120>] ? early_idt_handler_array+0x120/0x120
+	  [<ffffffff830ae053>] start_kernel+0x83/0x49a
+	  [<ffffffff830ad120>] ? early_idt_handler_array+0x120/0x120
+	  [<ffffffff830ad386>] x86_64_start_reservations+0x2a/0x2c
+	  [<ffffffff830ad4f3>] x86_64_start_kernel+0x16b/0x17a
+	 ================================================================================
+
+Usage
+-----
+
+To enable UBSAN configure kernel with:
+
+	CONFIG_UBSAN=y
+
+and to check the entire kernel:
+
+        CONFIG_UBSAN_SANITIZE_ALL=y
+
+To enable instrumentation for specific files or directories, add a line
+similar to the following to the respective kernel Makefile:
+
+        For a single file (e.g. main.o):
+                UBSAN_SANITIZE_main.o := y
+
+        For all files in one directory:
+                UBSAN_SANITIZE := y
+
+To exclude files from being instrumented even if
+CONFIG_UBSAN_SANITIZE_ALL=y, use:
+
+                UBSAN_SANITIZE_main.o := n
+        and:
+                UBSAN_SANITIZE := n
+
+Detection of unaligned accesses controlled through the separate option -
+CONFIG_UBSAN_ALIGNMENT. It's off by default on architectures that support
+unaligned accesses (CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y). One could
+still enable it in config, just note that it will produce a lot of UBSAN
+reports.
+
+References
+----------
+
+[1] - https://gcc.gnu.org/onlinedocs/gcc-4.9.0/gcc/Debugging-Options.html
+[2] - https://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html
diff --git a/Makefile b/Makefile
index 3a0234f..e32e96e 100644
--- a/Makefile
+++ b/Makefile
@@ -411,7 +411,7 @@  export MAKE AWK GENKSYMS INSTALLKERNEL PERL PYTHON UTS_MACHINE
 export HOSTCXX HOSTCXXFLAGS LDFLAGS_MODULE CHECK CHECKFLAGS
 
 export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS LDFLAGS
-export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE CFLAGS_GCOV CFLAGS_KASAN
+export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE CFLAGS_GCOV CFLAGS_KASAN CFLAGS_UBSAN
 export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE
 export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE
 export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL
@@ -778,6 +778,7 @@  endif
 
 include scripts/Makefile.kasan
 include scripts/Makefile.extrawarn
+include scripts/Makefile.ubsan
 
 # Add any arch overrides and user supplied CPPFLAGS, AFLAGS and CFLAGS as the
 # last assignments
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index db3622f..c892eb4 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -30,6 +30,7 @@  config X86
 	select ARCH_HAS_PMEM_API		if X86_64
 	select ARCH_HAS_MMIO_FLUSH
 	select ARCH_HAS_SG_CHAIN
+	select ARCH_HAS_UBSAN_SANTIZE_ALL
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select ARCH_MIGHT_HAVE_ACPI_PDC		if ACPI
 	select ARCH_MIGHT_HAVE_PC_PARPORT
diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
index 2ee62db..bbe1a62 100644
--- a/arch/x86/boot/Makefile
+++ b/arch/x86/boot/Makefile
@@ -60,6 +60,7 @@  clean-files += cpustr.h
 KBUILD_CFLAGS	:= $(USERINCLUDE) $(REALMODE_CFLAGS) -D_SETUP
 KBUILD_AFLAGS	:= $(KBUILD_CFLAGS) -D__ASSEMBLY__
 GCOV_PROFILE := n
+UBSAN_SANITIZE := n
 
 $(obj)/bzImage: asflags-y  := $(SVGA_MODE)
 
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 0a291cd..f9ce75d 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -33,6 +33,7 @@  KBUILD_CFLAGS += $(call cc-option,-fno-stack-protector)
 
 KBUILD_AFLAGS  := $(KBUILD_CFLAGS) -D__ASSEMBLY__
 GCOV_PROFILE := n
+UBSAN_SANITIZE :=n
 
 LDFLAGS := -m elf_$(UTS_MACHINE)
 LDFLAGS_vmlinux := -T
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index 265c0ed..c854541 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -4,6 +4,7 @@ 
 
 KBUILD_CFLAGS += $(DISABLE_LTO)
 KASAN_SANITIZE := n
+UBSAN_SANITIZE := n
 
 VDSO64-$(CONFIG_X86_64)		:= y
 VDSOX32-$(CONFIG_X86_X32_ABI)	:= y
diff --git a/arch/x86/realmode/rm/Makefile b/arch/x86/realmode/rm/Makefile
index 2730d77..3e75fcf 100644
--- a/arch/x86/realmode/rm/Makefile
+++ b/arch/x86/realmode/rm/Makefile
@@ -70,3 +70,4 @@  KBUILD_CFLAGS	:= $(LINUXINCLUDE) $(REALMODE_CFLAGS) -D_SETUP -D_WAKEUP \
 		   -I$(srctree)/arch/x86/boot
 KBUILD_AFLAGS	:= $(KBUILD_CFLAGS) -D__ASSEMBLY__
 GCOV_PROFILE := n
+UBSAN_SANITIZE := n
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index 3c0467d..b2a172d 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -22,6 +22,7 @@  KBUILD_CFLAGS			:= $(cflags-y) \
 
 GCOV_PROFILE			:= n
 KASAN_SANITIZE			:= n
+UBSAN_SANITIZE			:= n
 
 lib-y				:= efi-stub-helper.o
 
diff --git a/include/linux/sched.h b/include/linux/sched.h
index edad7a4..f4d2f2e 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1629,6 +1629,9 @@  struct task_struct {
 	struct held_lock held_locks[MAX_LOCK_DEPTH];
 	gfp_t lockdep_reclaim_gfp;
 #endif
+#ifdef CONFIG_UBSAN
+	unsigned int in_ubsan;
+#endif
 
 /* journalling filesystem info */
 	void *journal_info;
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 8c15b29..4bab98f 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1853,3 +1853,4 @@  source "samples/Kconfig"
 
 source "lib/Kconfig.kgdb"
 
+source "lib/Kconfig.ubsan"
diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
new file mode 100644
index 0000000..3c2868b
--- /dev/null
+++ b/lib/Kconfig.ubsan
@@ -0,0 +1,29 @@ 
+config ARCH_HAS_UBSAN_SANTIZE_ALL
+	bool
+
+config UBSAN
+	bool "Undefined behaviour sanity checker"
+	help
+	  This option enables undefined behaviour sanity checker
+	  Compile-time instrumentation is used to detect various undefined
+	  behaviours in runtime. Various types of checks may be enabled
+	  via boot parameter ubsan_handle (see: Documentation/ubsan.txt).
+
+config UBSAN_SANITIZE_ALL
+	bool "Enable instrumentation for the entire kernel"
+	depends on UBSAN
+	depends on ARCH_HAS_UBSAN_SANTIZE_ALL
+	default y
+	help
+	  This option activates instrumentation for the entire kernel.
+	  If you don't enable this option, you have to explicitly specify
+	  UBSAN_SANITIZE := y for the files/directories you want to check for UB.
+
+config UBSAN_ALIGNMENT
+	bool "Enable checking of pointers alignment"
+	depends on UBSAN
+	default y if !HAVE_EFFICIENT_UNALIGNED_ACCESS
+	help
+	  This option enables detection of unaligned memory accesses.
+	  Enabling this option on architectures that support unalligned
+	  accesses may produce a lot of false positives.
diff --git a/lib/Makefile b/lib/Makefile
index 7f1de26..e710b08 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -208,3 +208,6 @@  quiet_cmd_build_OID_registry = GEN     $@
 clean-files	+= oid_registry_data.c
 
 obj-$(CONFIG_UCS2_STRING) += ucs2_string.o
+obj-$(CONFIG_UBSAN) += ubsan.o
+
+UBSAN_SANITIZE_ubsan.o := n
diff --git a/lib/ubsan.c b/lib/ubsan.c
new file mode 100644
index 0000000..95b0981
--- /dev/null
+++ b/lib/ubsan.c
@@ -0,0 +1,452 @@ 
+/*
+ * UBSAN error reporting functions
+ *
+ * Copyright (c) 2014 Samsung Electronics Co., Ltd.
+ * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/bitops.h>
+#include <linux/bug.h>
+#include <linux/ctype.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/sched.h>
+
+#include "ubsan.h"
+
+const char *type_check_kinds[] = {
+	"load of",
+	"store to",
+	"reference binding to",
+	"member access within",
+	"member call on",
+	"constructor call on",
+	"downcast of",
+	"downcast of"
+};
+
+#define REPORTED_BIT 31
+
+#if (BITS_PER_LONG == 64) && defined(__BIG_ENDIAN)
+#define COLUMN_MASK (~(1U << REPORTED_BIT))
+#define LINE_MASK   (~0U)
+#else
+#define COLUMN_MASK   (~0U)
+#define LINE_MASK (~(1U << REPORTED_BIT))
+#endif
+
+#define VALUE_LENGTH 40
+
+static bool was_reported(struct source_location *location)
+{
+	return test_and_set_bit(REPORTED_BIT, &location->reported);
+}
+
+static void print_source_location(const char *prefix,
+				struct source_location *loc)
+{
+	pr_err("%s %s:%d:%d\n", prefix, loc->file_name,
+		loc->line & LINE_MASK, loc->column & COLUMN_MASK);
+}
+
+static bool suppress_report(struct source_location *loc)
+{
+	return current->in_ubsan || was_reported(loc);
+}
+
+static bool type_is_int(struct type_descriptor *type)
+{
+	return type->type_kind == type_kind_int;
+}
+
+static bool type_is_signed(struct type_descriptor *type)
+{
+	WARN_ON(!type_is_int(type));
+	return  type->type_info & 1;
+}
+
+static unsigned type_bit_width(struct type_descriptor *type)
+{
+	return 1 << (type->type_info >> 1);
+}
+
+static bool is_inline_int(struct type_descriptor *type)
+{
+	unsigned inline_bits = sizeof(unsigned long)*8;
+	unsigned bits = type_bit_width(type);
+
+	WARN_ON(!type_is_int(type));
+
+	return bits <= inline_bits;
+}
+
+static s_max get_signed_val(struct type_descriptor *type, unsigned long val)
+{
+	if (is_inline_int(type)) {
+		unsigned extra_bits = sizeof(s_max)*8 - type_bit_width(type);
+		return ((s_max)val) << extra_bits >> extra_bits;
+	}
+
+	if (type_bit_width(type) == 64)
+		return *(s64 *)val;
+
+	return *(s_max *)val;
+}
+
+static bool val_is_negative(struct type_descriptor *type, unsigned long val)
+{
+	return type_is_signed(type) && get_signed_val(type, val) < 0;
+}
+
+static u_max get_unsigned_val(struct type_descriptor *type, unsigned long val)
+{
+	if (is_inline_int(type))
+		return val;
+
+	if (type_bit_width(type) == 64)
+		return *(u64 *)val;
+
+	return *(u_max *)val;
+}
+
+static void val_to_string(char *str, size_t size, struct type_descriptor *type,
+	unsigned long value)
+{
+	u_max val = get_unsigned_val(type, value);
+
+	if (type_is_int(type)) {
+		if (IS_ENABLED(CONFIG_ARCH_SUPPORTS_INT128)
+			&& type_bit_width(type) == 128)
+			scnprintf(str, size, "0x%08x%08x%08x%08x",
+				(u32)(val >> 96),
+				(u32)(val >> 64),
+				(u32)(val >> 32),
+				(u32)(val));
+		else if (type_is_signed(type))
+			scnprintf(str, size, "%lld",
+				(s64)get_signed_val(type, value));
+		else
+			scnprintf(str, size, "%llu",
+				(u64)get_unsigned_val(type, value));
+	}
+}
+
+static bool location_is_valid(struct source_location *loc)
+{
+	return loc->file_name != NULL;
+}
+
+static DEFINE_SPINLOCK(report_lock);
+
+static void ubsan_prologue(struct source_location *location,
+			unsigned long *flags)
+{
+	current->in_ubsan++;
+	spin_lock_irqsave(&report_lock, *flags);
+
+	pr_err("========================================"
+		"========================================\n");
+	print_source_location("UBSAN: Undefined behaviour in", location);
+}
+
+static void ubsan_epilogue(unsigned long *flags)
+{
+	dump_stack();
+	pr_err("========================================"
+		"========================================\n");
+	spin_unlock_irqrestore(&report_lock, *flags);
+	current->in_ubsan--;
+}
+
+static void handle_overflow(struct overflow_data *data, unsigned long lhs,
+			unsigned long rhs, char op)
+{
+
+	struct type_descriptor *type = data->type;
+	unsigned long flags;
+	char lhs_val_str[VALUE_LENGTH];
+	char rhs_val_str[VALUE_LENGTH];
+
+	if (suppress_report(&data->location))
+		return;
+
+	ubsan_prologue(&data->location, &flags);
+
+	val_to_string(lhs_val_str, sizeof(lhs_val_str), type, lhs);
+	val_to_string(rhs_val_str, sizeof(rhs_val_str), type, rhs);
+	pr_err("%s integer overflow:\n",
+		type_is_signed(type) ? "signed" : "unsigned");
+	pr_err("%s %c %s cannot be represented in type %s\n",
+		lhs_val_str,
+		op,
+		rhs_val_str,
+		type->type_name);
+
+	ubsan_epilogue(&flags);
+}
+
+void __ubsan_handle_add_overflow(struct overflow_data *data,
+				unsigned long lhs,
+				unsigned long rhs)
+{
+
+	handle_overflow(data, lhs, rhs, '+');
+}
+EXPORT_SYMBOL(__ubsan_handle_add_overflow);
+
+void __ubsan_handle_sub_overflow(struct overflow_data *data,
+				unsigned long lhs,
+				unsigned long rhs)
+{
+	handle_overflow(data, lhs, rhs, '-');
+}
+EXPORT_SYMBOL(__ubsan_handle_sub_overflow);
+
+void __ubsan_handle_mul_overflow(struct overflow_data *data,
+				unsigned long lhs,
+				unsigned long rhs)
+{
+	handle_overflow(data, lhs, rhs, '*');
+}
+EXPORT_SYMBOL(__ubsan_handle_mul_overflow);
+
+void __ubsan_handle_negate_overflow(struct overflow_data *data,
+				unsigned long old_val)
+{
+	unsigned long flags;
+	char old_val_str[VALUE_LENGTH];
+
+	if (suppress_report(&data->location))
+		return;
+
+	ubsan_prologue(&data->location, &flags);
+
+	val_to_string(old_val_str, sizeof(old_val_str), data->type, old_val);
+
+	pr_err("negation of %s cannot be represented in type %s:\n",
+		old_val_str, data->type->type_name);
+
+	ubsan_epilogue(&flags);
+}
+EXPORT_SYMBOL(__ubsan_handle_negate_overflow);
+
+
+void __ubsan_handle_divrem_overflow(struct overflow_data *data,
+				unsigned long lhs,
+				unsigned long rhs)
+{
+	unsigned long flags;
+	char rhs_val_str[VALUE_LENGTH];
+
+	if (suppress_report(&data->location))
+		return;
+
+	ubsan_prologue(&data->location, &flags);
+
+	val_to_string(rhs_val_str, sizeof(rhs_val_str), data->type, rhs);
+
+	if (type_is_signed(data->type) && get_signed_val(data->type, rhs) == -1)
+		pr_err("division of %s by -1 cannot be represented in type %s\n",
+			rhs_val_str, data->type->type_name);
+	else
+		pr_err("division by zero\n");
+
+	ubsan_epilogue(&flags);
+}
+EXPORT_SYMBOL(__ubsan_handle_divrem_overflow);
+
+static void handle_null_ptr_deref(struct type_mismatch_data *data)
+{
+	unsigned long flags;
+
+	if (suppress_report(&data->location))
+		return;
+
+	ubsan_prologue(&data->location, &flags);
+
+	pr_err("%s null pointer of type %s\n",
+		type_check_kinds[data->type_check_kind],
+		data->type->type_name);
+
+	ubsan_epilogue(&flags);
+}
+
+static void handle_missaligned_access(struct type_mismatch_data *data,
+				unsigned long ptr)
+{
+	unsigned long flags;
+
+	if (suppress_report(&data->location))
+		return;
+
+	ubsan_prologue(&data->location, &flags);
+
+	pr_err("%s misaligned address %p for type %s\n",
+		type_check_kinds[data->type_check_kind],
+		(void *)ptr, data->type->type_name);
+	pr_err("which requires %ld byte alignment\n", data->alignment);
+
+	ubsan_epilogue(&flags);
+}
+
+static void handle_object_size_mismatch(struct type_mismatch_data *data,
+					unsigned long ptr)
+{
+	unsigned long flags;
+
+	if (suppress_report(&data->location))
+		return;
+
+	ubsan_prologue(&data->location, &flags);
+	pr_err("%s address %pk with insufficient space\n",
+		type_check_kinds[data->type_check_kind],
+		(void *) ptr);
+	pr_err("for an object of type %s\n", data->type->type_name);
+	ubsan_epilogue(&flags);
+}
+
+void __ubsan_handle_type_mismatch(struct type_mismatch_data *data,
+				unsigned long ptr)
+{
+
+	if (!ptr)
+		handle_null_ptr_deref(data);
+	else if (data->alignment && !IS_ALIGNED(ptr, data->alignment))
+		handle_missaligned_access(data, ptr);
+	else
+		handle_object_size_mismatch(data, ptr);
+}
+EXPORT_SYMBOL(__ubsan_handle_type_mismatch);
+
+void __ubsan_handle_nonnull_return(struct nonnull_return_data *data)
+{
+	unsigned long flags;
+
+	if (suppress_report(&data->location))
+		return;
+
+	ubsan_prologue(&data->location, &flags);
+
+	pr_err("null pointer returned from function declared to never return null\n");
+
+	if (location_is_valid(&data->attr_location))
+		print_source_location("returns_nonnull attribute specified in",
+				&data->attr_location);
+
+	ubsan_epilogue(&flags);
+}
+EXPORT_SYMBOL(__ubsan_handle_nonnull_return);
+
+void __ubsan_handle_vla_bound_not_positive(struct vla_bound_data *data,
+					unsigned long bound)
+{
+	unsigned long flags;
+	char bound_str[VALUE_LENGTH];
+
+	if (suppress_report(&data->location))
+		return;
+
+	ubsan_prologue(&data->location, &flags);
+
+	val_to_string(bound_str, sizeof(bound_str), data->type, bound);
+	pr_err("variable length array bound value %s <= 0\n", bound_str);
+
+	ubsan_epilogue(&flags);
+}
+EXPORT_SYMBOL(__ubsan_handle_vla_bound_not_positive);
+
+void __ubsan_handle_out_of_bounds(struct out_of_bounds_data *data,
+				unsigned long index)
+{
+	unsigned long flags;
+	char index_str[VALUE_LENGTH];
+
+	if (suppress_report(&data->location))
+		return;
+
+	ubsan_prologue(&data->location, &flags);
+
+	val_to_string(index_str, sizeof(index_str), data->index_type, index);
+	pr_err("index %s is out of range for type %s\n", index_str,
+		data->array_type->type_name);
+	ubsan_epilogue(&flags);
+}
+EXPORT_SYMBOL(__ubsan_handle_out_of_bounds);
+
+void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data,
+					unsigned long lhs, unsigned long rhs)
+{
+	unsigned long flags;
+	struct type_descriptor *rhs_type = data->rhs_type;
+	struct type_descriptor *lhs_type = data->lhs_type;
+	char rhs_str[VALUE_LENGTH];
+	char lhs_str[VALUE_LENGTH];
+
+	if (suppress_report(&data->location))
+		return;
+
+	ubsan_prologue(&data->location, &flags);
+
+	val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs);
+	val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs);
+
+	if (val_is_negative(rhs_type, rhs))
+		pr_err("shift exponent %s is negative\n", rhs_str);
+
+	else if (get_unsigned_val(rhs_type, rhs) >=
+		type_bit_width(lhs_type))
+		pr_err("shift exponent %s is to large for %u-bit type %s\n",
+			rhs_str,
+			type_bit_width(lhs_type),
+			lhs_type->type_name);
+	else if (val_is_negative(lhs_type, lhs))
+		pr_err("left shift of negative value %s\n",
+			lhs_str);
+	else
+		pr_err("left shift of %s by %s places cannot be"
+			" represented in type %s\n",
+			lhs_str, rhs_str,
+			lhs_type->type_name);
+
+	ubsan_epilogue(&flags);
+}
+EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
+
+void __ubsan_handle_builtin_unreachable(struct unreachable_data *data)
+{
+	unsigned long flags;
+
+	if (suppress_report(&data->location))
+		return;
+
+	ubsan_prologue(&data->location, &flags);
+	pr_err("calling __builtin_unreachable()\n");
+	ubsan_epilogue(&flags);
+}
+EXPORT_SYMBOL(__ubsan_handle_builtin_unreachable);
+
+void __ubsan_handle_load_invalid_value(struct invalid_value_data *data,
+				unsigned long val)
+{
+	unsigned long flags;
+	char val_str[VALUE_LENGTH];
+
+	if (suppress_report(&data->location))
+		return;
+
+	ubsan_prologue(&data->location, &flags);
+
+	val_to_string(val_str, sizeof(val_str), data->type, val);
+
+	pr_err("load of value %s is not a valid value for type %s\n",
+		val_str, data->type->type_name);
+
+	ubsan_epilogue(&flags);
+}
+EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);
diff --git a/lib/ubsan.h b/lib/ubsan.h
new file mode 100644
index 0000000..7407127
--- /dev/null
+++ b/lib/ubsan.h
@@ -0,0 +1,84 @@ 
+#ifndef _LIB_UBSAN_H
+#define _LIB_UBSAN_H
+
+enum {
+	type_kind_int = 0,
+	type_kind_float = 1,
+	type_unknown = 0xffff
+};
+
+struct type_descriptor {
+	u16 type_kind;
+	u16 type_info;
+	char type_name[1];
+};
+
+struct source_location {
+	const char *file_name;
+	union {
+		unsigned long reported;
+		struct {
+			u32 line;
+			u32 column;
+		};
+	};
+};
+
+struct overflow_data {
+	struct source_location location;
+	struct type_descriptor *type;
+};
+
+struct type_mismatch_data {
+	struct source_location location;
+	struct type_descriptor *type;
+	unsigned long alignment;
+	unsigned char type_check_kind;
+};
+
+struct nonnull_arg_data {
+	struct source_location location;
+	struct source_location attr_location;
+	int arg_index;
+};
+
+struct nonnull_return_data {
+	struct source_location location;
+	struct source_location attr_location;
+};
+
+struct vla_bound_data {
+	struct source_location location;
+	struct type_descriptor *type;
+};
+
+struct out_of_bounds_data {
+	struct source_location location;
+	struct type_descriptor *array_type;
+	struct type_descriptor *index_type;
+};
+
+struct shift_out_of_bounds_data {
+	struct source_location location;
+	struct type_descriptor *lhs_type;
+	struct type_descriptor *rhs_type;
+};
+
+struct unreachable_data {
+	struct source_location location;
+};
+
+struct invalid_value_data {
+	struct source_location location;
+	struct type_descriptor *type;
+};
+
+#ifdef CONFIG_ARCH_SUPPORTS_INT128
+typedef __int128 s_max;
+typedef unsigned __int128 u_max;
+#else
+typedef s64 s_max;
+typedef u64 u_max;
+#endif
+
+#endif
diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile
index 6471014..a61460d 100644
--- a/mm/kasan/Makefile
+++ b/mm/kasan/Makefile
@@ -1,4 +1,5 @@ 
 KASAN_SANITIZE := n
+UBSAN_SANITIZE_kasan.o := n
 
 CFLAGS_REMOVE_kasan.o = -pg
 # Function splitter causes unnecessary splits in __asan_load1/__asan_store1
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 79e8661..d7c2032 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -129,6 +129,12 @@  _c_flags += $(if $(patsubst n%,, \
 		$(CFLAGS_KASAN))
 endif
 
+ifeq ($(CONFIG_UBSAN),y)
+_c_flags += $(if $(patsubst n%,, \
+		$(UBSAN_SANITIZE_$(basetarget).o)$(UBSAN_SANITIZE)$(CONFIG_UBSAN_SANITIZE_ALL)), \
+		$(CFLAGS_UBSAN))
+endif
+
 # If building the kernel in a separate objtree expand all occurrences
 # of -Idir to -I$(srctree)/dir except for absolute paths (starting with '/').
 
diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
new file mode 100644
index 0000000..0a0b36d
--- /dev/null
+++ b/scripts/Makefile.ubsan
@@ -0,0 +1,18 @@ 
+ifdef CONFIG_UBSAN
+      CFLAGS_UBSAN += $(call cc-option, -fsanitize=shift)
+      CFLAGS_UBSAN += $(call cc-option, -fsanitize=integer-divide-by-zero)
+      CFLAGS_UBSAN += $(call cc-option, -fsanitize=unreachable)
+      CFLAGS_UBSAN += $(call cc-option, -fsanitize=vla-bound)
+      CFLAGS_UBSAN += $(call cc-option, -fsanitize=null)
+      CFLAGS_UBSAN += $(call cc-option, -fsanitize=signed-integer-overflow)
+      CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds)
+      CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds-strict)
+      CFLAGS_UBSAN += $(call cc-option, -fsanitize=object-size)
+      CFLAGS_UBSAN += $(call cc-option, -fsanitize=returns-nonnull-attribute)
+      CFLAGS_UBSAN += $(call cc-option, -fsanitize=bool)
+      CFLAGS_UBSAN += $(call cc-option, -fsanitize=enum)
+
+ifdef CONFIG_UBSAN_ALIGNMENT
+      CFLAGS_UBSAN += $(call cc-option, -fsanitize=alignment)
+endif
+endif