[PATCH v4 0/3] UBSAN: run-time undefined behavior sanity checker

[PATCH v4 0/3] UBSAN: run-time undefined behavior sanity checker

[Andrey Ryabinin]

UBSAN is run-time undefined behaviour checker. It 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.


Changes since v3:
   - Fixed build failure/warnings reported by kbuild robot.
   - Fixed typo per Sasha.

Changes since V2:
   - Dropped -fsanitize=nonnull-attribute. It checks whether null values
     are not passed to arguments marked as requiring a non-null value by
     the "nonnull" function attribute.

     We don't have much functions with such attribute (early_shadow_write() in arch/blackfin
     and GCC builtin functions: memcpy, memset, memmove, etc). Some kernel code deliberately
     passes NULL-ptr with 0-length to mem*(). This should be fine since we compile kernel
     with -fno-delete-null-pointer-checks. And NULL-ptr with != 0 length will just crash.
     So this options is useless in kernel since it produces only false positives.
     See also: http://thread.gmane.org/gmane.linux.kernel/1810656
       

   - Also dropped enabling/disabling various checkers via boot cmdline.
     Boot time flag only disable reports, it can't disable compile-time code instrumentation.
     Thus, if we ever will need to disable some checker it would be better to
     do it in compile time via Kconfig option.

   - Alignment checks produce too much noise if CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is set.
      Since there is no boottime option to disable alignment checks, CONFIG_UBSAN_ALIGNMENT
      was added. It's off by default if CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is set.
   
   - Couple other small misc changes/fixes.



Changes since v1:
   - Refactoring and cleanups in lib/ubsan.c including Sasha's complains.
   - Some spelling fixes from Randy
   - Fixed possible memory corruption on 64 big endian machines, spotted by Rasmus.
   - Links to the relevant GCC documentation added into changelog (Peter).
   - Added documentation.
   - Fix deadlock caused by kernel/printk/printk.c instrumentation
        (patch "kernel: printk: specify alignment for struct printk_log").
   - Dropped useless 'Indirect call of a function through a function pointer of the wrong type'
     checker. GCC doesn't support this, and as clang manual says it's for C++ only.
   - Added checker for __builtin_unreachable() calls.
   - Removed redundant -fno-sanitize=float-cast-overflow from CFLAGS.
   - Added lock to prevent mixing reports.


Andrey Ryabinin (3):
  kernel: printk: specify alignment for struct printk_log
  mac80211: Prevent build failure with CONFIG_UBSAN=y
  UBSAN: run-time undefined behavior sanity checker

 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 +
 kernel/printk/printk.c                |  10 +-
 lib/Kconfig.debug                     |   1 +
 lib/Kconfig.ubsan                     |  29 +++
 lib/Makefile                          |   3 +
 lib/ubsan.c                           | 456 ++++++++++++++++++++++++++++++++++
 lib/ubsan.h                           |  84 +++++++
 mm/kasan/Makefile                     |   1 +
 net/mac80211/debugfs.c                |   7 +-
 scripts/Makefile.lib                  |   6 +
 scripts/Makefile.ubsan                |  18 ++
 19 files changed, 700 insertions(+), 11 deletions(-)
 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

-- 
2.4.10

[PATCH v4 0/3] UBSAN: run-time undefined behavior sanity checker

[Andrey Ryabinin]

UBSAN is run-time undefined behaviour checker. It 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.


Changes since v3:
   - Fixed build failure/warnings reported by kbuild robot.
   - Fixed typo per Sasha.

Changes since V2:
   - Dropped -fsanitize=nonnull-attribute. It checks whether null values
     are not passed to arguments marked as requiring a non-null value by
     the "nonnull" function attribute.

     We don't have much functions with such attribute (early_shadow_write() in arch/blackfin
     and GCC builtin functions: memcpy, memset, memmove, etc). Some kernel code deliberately
     passes NULL-ptr with 0-length to mem*(). This should be fine since we compile kernel
     with -fno-delete-null-pointer-checks. And NULL-ptr with != 0 length will just crash.
     So this options is useless in kernel since it produces only false positives.
     See also: http://thread.gmane.org/gmane.linux.kernel/1810656
       

   - Also dropped enabling/disabling various checkers via boot cmdline.
     Boot time flag only disable reports, it can't disable compile-time code instrumentation.
     Thus, if we ever will need to disable some checker it would be better to
     do it in compile time via Kconfig option.

   - Alignment checks produce too much noise if CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is set.
      Since there is no boottime option to disable alignment checks, CONFIG_UBSAN_ALIGNMENT
      was added. It's off by default if CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is set.
   
   - Couple other small misc changes/fixes.



Changes since v1:
   - Refactoring and cleanups in lib/ubsan.c including Sasha's complains.
   - Some spelling fixes from Randy
   - Fixed possible memory corruption on 64 big endian machines, spotted by Rasmus.
   - Links to the relevant GCC documentation added into changelog (Peter).
   - Added documentation.
   - Fix deadlock caused by kernel/printk/printk.c instrumentation
        (patch "kernel: printk: specify alignment for struct printk_log").
   - Dropped useless 'Indirect call of a function through a function pointer of the wrong type'
     checker. GCC doesn't support this, and as clang manual says it's for C++ only.
   - Added checker for __builtin_unreachable() calls.
   - Removed redundant -fno-sanitize=float-cast-overflow from CFLAGS.
   - Added lock to prevent mixing reports.


Andrey Ryabinin (3):
  kernel: printk: specify alignment for struct printk_log
  mac80211: Prevent build failure with CONFIG_UBSAN=y
  UBSAN: run-time undefined behavior sanity checker

 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 +
 kernel/printk/printk.c                |  10 +-
 lib/Kconfig.debug                     |   1 +
 lib/Kconfig.ubsan                     |  29 +++
 lib/Makefile                          |   3 +
 lib/ubsan.c                           | 456 ++++++++++++++++++++++++++++++++++
 lib/ubsan.h                           |  84 +++++++
 mm/kasan/Makefile                     |   1 +
 net/mac80211/debugfs.c                |   7 +-
 scripts/Makefile.lib                  |   6 +
 scripts/Makefile.ubsan                |  18 ++
 19 files changed, 700 insertions(+), 11 deletions(-)
 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

-- 
2.4.10

[PATCH v4 1/3] kernel: printk: specify alignment for struct printk_log

[Andrey Ryabinin]

On architectures that have support for efficient unaligned access
struct printk_log has 4-byte alignment.
Specify alignment attribute in type declaration.

The whole point of this patch is to fix deadlock which happening
when UBSAN detects unaligned access in printk() thus UBSAN recursively
calls printk() with logbuf_lock held by top printk() call.

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
---
 kernel/printk/printk.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 0c9f0250..8712409 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -233,7 +233,11 @@ struct printk_log {
 	u8 facility;		/* syslog facility */
 	u8 flags:5;		/* internal record flags */
 	u8 level:3;		/* syslog level */
-};
+}
+#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+__packed __aligned(4)
+#endif
+;
 
 /*
  * The logbuf_lock protects kmsg buffer, indices, counters.  This can be taken
@@ -274,11 +278,7 @@ static u32 clear_idx;
 #define LOG_FACILITY(v)		((v) >> 3 & 0xff)
 
 /* record buffer */
-#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
-#define LOG_ALIGN 4
-#else
 #define LOG_ALIGN __alignof__(struct printk_log)
-#endif
 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
 static char *log_buf = __log_buf;
-- 
2.4.10

[PATCH v4 1/3] kernel: printk: specify alignment for struct printk_log

[Andrey Ryabinin]

On architectures that have support for efficient unaligned access
struct printk_log has 4-byte alignment.
Specify alignment attribute in type declaration.

The whole point of this patch is to fix deadlock which happening
when UBSAN detects unaligned access in printk() thus UBSAN recursively
calls printk() with logbuf_lock held by top printk() call.

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
---
 kernel/printk/printk.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 0c9f0250..8712409 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -233,7 +233,11 @@ struct printk_log {
 	u8 facility;		/* syslog facility */
 	u8 flags:5;		/* internal record flags */
 	u8 level:3;		/* syslog level */
-};
+}
+#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+__packed __aligned(4)
+#endif
+;
 
 /*
  * The logbuf_lock protects kmsg buffer, indices, counters.  This can be taken
@@ -274,11 +278,7 @@ static u32 clear_idx;
 #define LOG_FACILITY(v)		((v) >> 3 & 0xff)
 
 /* record buffer */
-#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
-#define LOG_ALIGN 4
-#else
 #define LOG_ALIGN __alignof__(struct printk_log)
-#endif
 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
 static char *log_buf = __log_buf;
-- 
2.4.10

[PATCH v4 2/3] mac80211: Prevent build failure with CONFIG_UBSAN=y

[Andrey Ryabinin]

With upcoming CONFIG_UBSAN the following BUILD_BUG_ON in
net/mac80211/debugfs.c starts to trigger:
	BUILD_BUG_ON(hw_flag_names[NUM_IEEE80211_HW_FLAGS] != (void *)0x1);

It seems, that compiler instrumentation causes some code deoptimizations.
Because of that GCC is not being able to resolve condition in BUILD_BUG_ON()
at compile time.

We could make size of hw_flag_names array unspecified and replace the
condition in BUILD_BUG_ON() with following:
	ARRAY_SIZE(hw_flag_names) != NUM_IEEE80211_HW_FLAGS

That will have the same effect as before (adding new flag without updating
array will trigger build failure) except it doesn't fail with CONFIG_UBSAN.
As a bonus this patch slightly decreases size of hw_flag_names array.

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: "David S. Miller" <davem@davemloft.net>
---
 net/mac80211/debugfs.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/net/mac80211/debugfs.c b/net/mac80211/debugfs.c
index abbdff0..3e24d0d 100644
--- a/net/mac80211/debugfs.c
+++ b/net/mac80211/debugfs.c
@@ -91,7 +91,7 @@ static const struct file_operations reset_ops = {
 };
 #endif
 
-static const char *hw_flag_names[NUM_IEEE80211_HW_FLAGS + 1] = {
+static const char *hw_flag_names[] = {
 #define FLAG(F)	[IEEE80211_HW_##F] = #F
 	FLAG(HAS_RATE_CONTROL),
 	FLAG(RX_INCLUDES_FCS),
@@ -126,9 +126,6 @@ static const char *hw_flag_names[NUM_IEEE80211_HW_FLAGS + 1] = {
 	FLAG(SUPPORTS_AMSDU_IN_AMPDU),
 	FLAG(BEACON_TX_STATUS),
 	FLAG(NEEDS_UNIQUE_STA_ADDR),
-
-	/* keep last for the build bug below */
-	(void *)0x1
 #undef FLAG
 };
 
@@ -148,7 +145,7 @@ static ssize_t hwflags_read(struct file *file, char __user *user_buf,
 	/* fail compilation if somebody adds or removes
 	 * a flag without updating the name array above
 	 */
-	BUILD_BUG_ON(hw_flag_names[NUM_IEEE80211_HW_FLAGS] != (void *)0x1);
+	BUILD_BUG_ON(ARRAY_SIZE(hw_flag_names) != NUM_IEEE80211_HW_FLAGS);
 
 	for (i = 0; i < NUM_IEEE80211_HW_FLAGS; i++) {
 		if (test_bit(i, local->hw.flags))
-- 
2.4.10

[PATCH v4 2/3] mac80211: Prevent build failure with CONFIG_UBSAN=y

[Andrey Ryabinin]

With upcoming CONFIG_UBSAN the following BUILD_BUG_ON in
net/mac80211/debugfs.c starts to trigger:
	BUILD_BUG_ON(hw_flag_names[NUM_IEEE80211_HW_FLAGS] != (void *)0x1);

It seems, that compiler instrumentation causes some code deoptimizations.
Because of that GCC is not being able to resolve condition in BUILD_BUG_ON()
at compile time.

We could make size of hw_flag_names array unspecified and replace the
condition in BUILD_BUG_ON() with following:
	ARRAY_SIZE(hw_flag_names) != NUM_IEEE80211_HW_FLAGS

That will have the same effect as before (adding new flag without updating
array will trigger build failure) except it doesn't fail with CONFIG_UBSAN.
As a bonus this patch slightly decreases size of hw_flag_names array.

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: "David S. Miller" <davem@davemloft.net>
---
 net/mac80211/debugfs.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/net/mac80211/debugfs.c b/net/mac80211/debugfs.c
index abbdff0..3e24d0d 100644
--- a/net/mac80211/debugfs.c
+++ b/net/mac80211/debugfs.c
@@ -91,7 +91,7 @@ static const struct file_operations reset_ops = {
 };
 #endif
 
-static const char *hw_flag_names[NUM_IEEE80211_HW_FLAGS + 1] = {
+static const char *hw_flag_names[] = {
 #define FLAG(F)	[IEEE80211_HW_##F] = #F
 	FLAG(HAS_RATE_CONTROL),
 	FLAG(RX_INCLUDES_FCS),
@@ -126,9 +126,6 @@ static const char *hw_flag_names[NUM_IEEE80211_HW_FLAGS + 1] = {
 	FLAG(SUPPORTS_AMSDU_IN_AMPDU),
 	FLAG(BEACON_TX_STATUS),
 	FLAG(NEEDS_UNIQUE_STA_ADDR),
-
-	/* keep last for the build bug below */
-	(void *)0x1
 #undef FLAG
 };
 
@@ -148,7 +145,7 @@ static ssize_t hwflags_read(struct file *file, char __user *user_buf,
 	/* fail compilation if somebody adds or removes
 	 * a flag without updating the name array above
 	 */
-	BUILD_BUG_ON(hw_flag_names[NUM_IEEE80211_HW_FLAGS] != (void *)0x1);
+	BUILD_BUG_ON(ARRAY_SIZE(hw_flag_names) != NUM_IEEE80211_HW_FLAGS);
 
 	for (i = 0; i < NUM_IEEE80211_HW_FLAGS; i++) {
 		if (test_bit(i, local->hw.flags))
-- 
2.4.10

[PATCH v4 3/3] UBSAN: run-time undefined behavior sanity checker

[Andrey Ryabinin]

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                           | 456 ++++++++++++++++++++++++++++++++++
 lib/ubsan.h                           |  84 +++++++
 mm/kasan/Makefile                     |   1 +
 scripts/Makefile.lib                  |   6 +
 scripts/Makefile.ubsan                |  18 ++
 17 files changed, 693 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

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 b49b551..b8e0923 100644
--- a/Makefile
+++ b/Makefile
@@ -416,7 +416,7 @@ 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
@@ -795,6 +795,7 @@ endif
 include scripts/Makefile.kasan
 include scripts/Makefile.extrawarn
 include scripts/Makefile.lto
+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 c989d5b..9bcf6b5 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 f425aac..418af55 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 334a3c2..b60cf17 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1882,3 +1882,4 @@ 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 67945a4..736098f 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -211,3 +211,6 @@ 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..3914357
--- /dev/null
+++ b/lib/ubsan.c
@@ -0,0 +1,456 @@
+/*
+ * 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 (type_bit_width(type) == 128) {
+#ifdef CONFIG_ARCH_SUPPORTS_INT128
+			scnprintf(str, size, "0x%08x%08x%08x%08x",
+				(u32)(val >> 96),
+				(u32)(val >> 64),
+				(u32)(val >> 32),
+				(u32)(val));
+#else
+			WARN_ON(1);
+#endif
+		} 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 too 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 e18957b..78bc5d3 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
-- 
2.4.10

[PATCH v4 3/3] UBSAN: run-time undefined behavior sanity checker

[Andrey Ryabinin]

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                           | 456 ++++++++++++++++++++++++++++++++++
 lib/ubsan.h                           |  84 +++++++
 mm/kasan/Makefile                     |   1 +
 scripts/Makefile.lib                  |   6 +
 scripts/Makefile.ubsan                |  18 ++
 17 files changed, 693 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

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 b49b551..b8e0923 100644
--- a/Makefile
+++ b/Makefile
@@ -416,7 +416,7 @@ 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
@@ -795,6 +795,7 @@ endif
 include scripts/Makefile.kasan
 include scripts/Makefile.extrawarn
 include scripts/Makefile.lto
+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 c989d5b..9bcf6b5 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 f425aac..418af55 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 334a3c2..b60cf17 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1882,3 +1882,4 @@ 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 67945a4..736098f 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -211,3 +211,6 @@ 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..3914357
--- /dev/null
+++ b/lib/ubsan.c
@@ -0,0 +1,456 @@
+/*
+ * 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 (type_bit_width(type) == 128) {
+#ifdef CONFIG_ARCH_SUPPORTS_INT128
+			scnprintf(str, size, "0x%08x%08x%08x%08x",
+				(u32)(val >> 96),
+				(u32)(val >> 64),
+				(u32)(val >> 32),
+				(u32)(val));
+#else
+			WARN_ON(1);
+#endif
+		} 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 too 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 e18957b..78bc5d3 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
-- 
2.4.10

Re: [PATCH v4 2/3] mac80211: Prevent build failure with CONFIG_UBSAN=y

[Johannes Berg]

On Thu, 2015-12-03 at 18:50 +0300, Andrey Ryabinin wrote:
> With upcoming CONFIG_UBSAN the following BUILD_BUG_ON in
> net/mac80211/debugfs.c starts to trigger:
> 	BUILD_BUG_ON(hw_flag_names[NUM_IEEE80211_HW_FLAGS] != (void
> *)0x1);
> 
> It seems, that compiler instrumentation causes some code
> deoptimizations.
> Because of that GCC is not being able to resolve condition in
> BUILD_BUG_ON()
> at compile time.
> 
> We could make size of hw_flag_names array unspecified and replace the
> condition in BUILD_BUG_ON() with following:
> 	ARRAY_SIZE(hw_flag_names) != NUM_IEEE80211_HW_FLAGS
> 
> That will have the same effect as before (adding new flag without
> updating
> array will trigger build failure) except it doesn't fail with
> CONFIG_UBSAN.
> As a bonus this patch slightly decreases size of hw_flag_names array.
> 
Seems fine, would you want to take it through some other tree together
with UBSAN, or do you expect that to still take long enough to allow
this to trickle through our trees?

johannes

Re: [PATCH v4 2/3] mac80211: Prevent build failure with CONFIG_UBSAN=y

[Andrey Ryabinin]

2015-12-03 20:05 GMT+03:00 Johannes Berg <johannes@sipsolutions.net>:
> On Thu, 2015-12-03 at 18:50 +0300, Andrey Ryabinin wrote:
>> With upcoming CONFIG_UBSAN the following BUILD_BUG_ON in
>> net/mac80211/debugfs.c starts to trigger:
>>       BUILD_BUG_ON(hw_flag_names[NUM_IEEE80211_HW_FLAGS] != (void
>> *)0x1);
>>
>> It seems, that compiler instrumentation causes some code
>> deoptimizations.
>> Because of that GCC is not being able to resolve condition in
>> BUILD_BUG_ON()
>> at compile time.
>>
>> We could make size of hw_flag_names array unspecified and replace the
>> condition in BUILD_BUG_ON() with following:
>>       ARRAY_SIZE(hw_flag_names) != NUM_IEEE80211_HW_FLAGS
>>
>> That will have the same effect as before (adding new flag without
>> updating
>> array will trigger build failure) except it doesn't fail with
>> CONFIG_UBSAN.
>> As a bonus this patch slightly decreases size of hw_flag_names array.
>>
> Seems fine, would you want to take it through some other tree together
> with UBSAN, or do you expect that to still take long enough to allow
> this to trickle through our trees?
>

I expect that Andrew will take it with UBSAN for 4.5

Re: [PATCH v4 3/3] UBSAN: run-time undefined behavior sanity checker

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 1560 bytes --]

Hi Andrey,

[auto build test WARNING on next-20151203]
[cannot apply to tip/x86/core kbuild/rc-fixes v4.4-rc3 v4.4-rc2 v4.4-rc1 v4.4-rc3]

url:    https://github.com/0day-ci/linux/commits/Andrey-Ryabinin/UBSAN-run-time-undefined-behavior-sanity-checker/20151204-202547
config: i386-allmodconfig (attached as .config)
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All warnings (new ones prefixed by >>):

   lib/ubsan.c: In function 'val_to_string':
>> lib/ubsan.c:121:8: warning: unused variable 'val' [-Wunused-variable]
     u_max val = get_unsigned_val(type, value);
           ^

vim +/val +121 lib/ubsan.c

   105	}
   106	
   107	static u_max get_unsigned_val(struct type_descriptor *type, unsigned long val)
   108	{
   109		if (is_inline_int(type))
   110			return val;
   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 (type_bit_width(type) == 128) {
   125	#ifdef CONFIG_ARCH_SUPPORTS_INT128
   126				scnprintf(str, size, "0x%08x%08x%08x%08x",
   127					(u32)(val >> 96),
   128					(u32)(val >> 64),
   129					(u32)(val >> 32),

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

[-- Attachment #2: .config.gz --]
[-- Type: application/octet-stream, Size: 53045 bytes --]

Re: [PATCH v4 3/3] UBSAN: run-time undefined behavior sanity checker

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 1560 bytes --]

Hi Andrey,

[auto build test WARNING on next-20151203]
[cannot apply to tip/x86/core kbuild/rc-fixes v4.4-rc3 v4.4-rc2 v4.4-rc1 v4.4-rc3]

url:    https://github.com/0day-ci/linux/commits/Andrey-Ryabinin/UBSAN-run-time-undefined-behavior-sanity-checker/20151204-202547
config: i386-allmodconfig (attached as .config)
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All warnings (new ones prefixed by >>):

   lib/ubsan.c: In function 'val_to_string':
>> lib/ubsan.c:121:8: warning: unused variable 'val' [-Wunused-variable]
     u_max val = get_unsigned_val(type, value);
           ^

vim +/val +121 lib/ubsan.c

   105	}
   106	
   107	static u_max get_unsigned_val(struct type_descriptor *type, unsigned long val)
   108	{
   109		if (is_inline_int(type))
   110			return val;
   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 (type_bit_width(type) == 128) {
   125	#ifdef CONFIG_ARCH_SUPPORTS_INT128
   126				scnprintf(str, size, "0x%08x%08x%08x%08x",
   127					(u32)(val >> 96),
   128					(u32)(val >> 64),
   129					(u32)(val >> 32),

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

[-- Attachment #2: .config.gz --]
[-- Type: application/octet-stream, Size: 53045 bytes --]

Re: [PATCH v4 0/3] UBSAN: run-time undefined behavior sanity checker

[Andrew Morton]

On Thu, 3 Dec 2015 18:50:04 +0300 Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:

> UBSAN is run-time undefined behaviour checker. It 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.

What I'd like to see in this changelog is a description of any kernel
issues which this checker has already identified: what were they and
what was their potential impact at runtime.

This info will help us to understand the value of the proposed feature.

Thanks.

Re: [PATCH v4 0/3] UBSAN: run-time undefined behavior sanity checker

[Andrew Morton]

On Thu, 3 Dec 2015 18:50:04 +0300 Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:

> UBSAN is run-time undefined behaviour checker. It 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.

What I'd like to see in this changelog is a description of any kernel
issues which this checker has already identified: what were they and
what was their potential impact at runtime.

This info will help us to understand the value of the proposed feature.

Thanks.

Re: [PATCH v4 3/3] UBSAN: run-time undefined behavior sanity checker

[Andrew Morton]

On Fri, 4 Dec 2015 22:27:36 +0800 kbuild test robot <lkp@intel.com> wrote:

> [auto build test WARNING on next-20151203]
> [cannot apply to tip/x86/core kbuild/rc-fixes v4.4-rc3 v4.4-rc2 v4.4-rc1 v4.4-rc3]
> 
> url:    https://github.com/0day-ci/linux/commits/Andrey-Ryabinin/UBSAN-run-time-undefined-behavior-sanity-checker/20151204-202547
> config: i386-allmodconfig (attached as .config)
> reproduce:
>         # save the attached .config to linux build tree
>         make ARCH=i386 
> 
> All warnings (new ones prefixed by >>):
> 
>    lib/ubsan.c: In function 'val_to_string':
> >> lib/ubsan.c:121:8: warning: unused variable 'val' [-Wunused-variable]
>      u_max val = get_unsigned_val(type, value);

I did this.

--- a/lib/ubsan.c~ubsan-run-time-undefined-behavior-sanity-checker-fix
+++ a/lib/ubsan.c
@@ -118,11 +118,11 @@ static u_max get_unsigned_val(struct typ
 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 (type_bit_width(type) == 128) {
 #ifdef CONFIG_ARCH_SUPPORTS_INT128
+			u_max val = get_unsigned_val(type, value);
+
 			scnprintf(str, size, "0x%08x%08x%08x%08x",
 				(u32)(val >> 96),
 				(u32)(val >> 64),

Re: [PATCH v4 0/3] UBSAN: run-time undefined behavior sanity checker

[Andrey Ryabinin]

On 12/05/2015 03:37 AM, Andrew Morton wrote:
> On Thu, 3 Dec 2015 18:50:04 +0300 Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:
> 
>> UBSAN is run-time undefined behaviour checker. It 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.
> 
> What I'd like to see in this changelog is a description of any kernel
> issues which this checker has already identified: what were they and
> what was their potential impact at runtime.
> 
> This info will help us to understand the value of the proposed feature.
> 

Sure, I'll come back soon with a list of found bugs.

> Thanks.
> 

Re: [PATCH v4 0/3] UBSAN: run-time undefined behavior sanity checker

[Andrey Ryabinin]

On 12/05/2015 03:37 AM, Andrew Morton wrote:
> On Thu, 3 Dec 2015 18:50:04 +0300 Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:
> 
>> UBSAN is run-time undefined behaviour checker. It 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.
> 
> What I'd like to see in this changelog is a description of any kernel
> issues which this checker has already identified: what were they and
> what was their potential impact at runtime.
> 
> This info will help us to understand the value of the proposed feature.
> 

Sure, I'll come back soon with a list of found bugs.

> Thanks.
> 

Re: [PATCH v4 3/3] UBSAN: run-time undefined behavior sanity checker

[Andrew Morton]

On Thu, 3 Dec 2015 18:50:07 +0300 Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:

> 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.
> 
> ...
>
> +#ifdef CONFIG_ARCH_SUPPORTS_INT128
> +typedef __int128 s_max;
> +typedef unsigned __int128 u_max;
> +#else

In file included from lib/ubsan.c:21:
lib/ubsan.h:77: error: expected '=', ',', ';', 'asm' or '__attribute__' before 's_max'
lib/ubsan.h:78: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'u_max'
lib/ubsan.c:89: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'get_signed_val'


gcc-4.4.4 doesn't appear to like __int128.  The only other use of
__int128 is include/linux/math64.h:mul_u64_u32_shr() and it uses
defined(__SIZEOF_INT128__) as well.

Using that gives me

lib/ubsan.c: In function 'val_to_string':
lib/ubsan.c:127: warning: right shift count >= width of type
lib/ubsan.c:128: warning: right shift count >= width of type

so I bodged that site too.  I need to get an mmotm release out the door.


--- a/lib/ubsan.c~ubsan-run-time-undefined-behavior-sanity-checker-fix-3
+++ a/lib/ubsan.c
@@ -120,7 +120,7 @@ static void val_to_string(char *str, siz
 {
 	if (type_is_int(type)) {
 		if (type_bit_width(type) == 128) {
-#ifdef CONFIG_ARCH_SUPPORTS_INT128
+#if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
 			u_max val = get_unsigned_val(type, value);
 
 			scnprintf(str, size, "0x%08x%08x%08x%08x",
--- a/lib/ubsan.h~ubsan-run-time-undefined-behavior-sanity-checker-fix-3
+++ a/lib/ubsan.h
@@ -73,7 +73,7 @@ struct invalid_value_data {
 	struct type_descriptor *type;
 };
 
-#ifdef CONFIG_ARCH_SUPPORTS_INT128
+#if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
 typedef __int128 s_max;
 typedef unsigned __int128 u_max;
 #else
_

Re: [PATCH v4 3/3] UBSAN: run-time undefined behavior sanity checker

[Andrew Morton]

On Thu, 3 Dec 2015 18:50:07 +0300 Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:

> 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.
> 
> ...
>
> +#ifdef CONFIG_ARCH_SUPPORTS_INT128
> +typedef __int128 s_max;
> +typedef unsigned __int128 u_max;
> +#else

In file included from lib/ubsan.c:21:
lib/ubsan.h:77: error: expected '=', ',', ';', 'asm' or '__attribute__' before 's_max'
lib/ubsan.h:78: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'u_max'
lib/ubsan.c:89: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'get_signed_val'


gcc-4.4.4 doesn't appear to like __int128.  The only other use of
__int128 is include/linux/math64.h:mul_u64_u32_shr() and it uses
defined(__SIZEOF_INT128__) as well.

Using that gives me

lib/ubsan.c: In function 'val_to_string':
lib/ubsan.c:127: warning: right shift count >= width of type
lib/ubsan.c:128: warning: right shift count >= width of type

so I bodged that site too.  I need to get an mmotm release out the door.


--- a/lib/ubsan.c~ubsan-run-time-undefined-behavior-sanity-checker-fix-3
+++ a/lib/ubsan.c
@@ -120,7 +120,7 @@ static void val_to_string(char *str, siz
 {
 	if (type_is_int(type)) {
 		if (type_bit_width(type) == 128) {
-#ifdef CONFIG_ARCH_SUPPORTS_INT128
+#if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
 			u_max val = get_unsigned_val(type, value);
 
 			scnprintf(str, size, "0x%08x%08x%08x%08x",
--- a/lib/ubsan.h~ubsan-run-time-undefined-behavior-sanity-checker-fix-3
+++ a/lib/ubsan.h
@@ -73,7 +73,7 @@ struct invalid_value_data {
 	struct type_descriptor *type;
 };
 
-#ifdef CONFIG_ARCH_SUPPORTS_INT128
+#if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
 typedef __int128 s_max;
 typedef unsigned __int128 u_max;
 #else
_

Re: [PATCH v4 3/3] UBSAN: run-time undefined behavior sanity checker

[Daniel Axtens]

Hi Andrey,

>+	select ARCH_HAS_UBSAN_SANTIZE_ALL

I think you've missed an I in SAN*I*TIZE here.

Apart from that, I've tested that this works on PowerPC, so:
Tested-by: Daniel Axtens <dja@axtens.net> # on PowerPC only

Regards,
Daniel

Re: [PATCH v4 0/3] UBSAN: run-time undefined behavior sanity checker

[Andrey Ryabinin]

On 12/05/2015 03:37 AM, Andrew Morton wrote:
> On Thu, 3 Dec 2015 18:50:04 +0300 Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:
> 
>> UBSAN is run-time undefined behaviour checker. It 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.
> 
> What I'd like to see in this changelog is a description of any kernel
> issues which this checker has already identified: what were they and
> what was their potential impact at runtime.
> 
> This info will help us to understand the value of the proposed feature.
> 


It's hard for me to judge about runtime impact of those bugs,
as don't know much about what that bugged code is doing.
Frankly speaking, nothing looks too scary for me, although some bugs would
be hard to find without UBSAN.


Found bugs:

	* out-of-bounds access - 97840cb67ff5 ("netfilter: nfnetlink: fix insufficient validation in nfnetlink_bind")

undefined shifts:
	* d48458d4a768 ("jbd2: use a better hash function for the revoke table")
	* 10632008b9e1 ("clockevents: Prevent shift out of bounds")
	* 'x << -1' shift in ext4 - http://lkml.kernel.org/r/<5444EF21.8020501@samsung.com>
	* undefined rol32(0) - http://lkml.kernel.org/r/<1449198241-20654-1-git-send-email-sasha.levin@oracle.com>
	* undefined dirty_ratelimit calculation - http://lkml.kernel.org/r/<566594E2.3050306@odin.com>
	* undefined roundown_pow_of_two(0) - http://lkml.kernel.org/r/<1449156616-11474-1-git-send-email-sasha.levin@oracle.com>
	* [WONTFIX] undefined shift in __bpf_prog_run - http://lkml.kernel.org/r/<CACT4Y+ZxoR3UjLgcNdUm4fECLMx2VdtfrENMtRRCdgHB2n0bJA@mail.gmail.com>
		WONTFIX here because it should be fixed in bpf program, not in kernel.

signed overflows:
	* 32a8df4e0b33f ("sched: Fix odd values in effective_load() calculations")
	* mul overflow in ntp - http://lkml.kernel.org/r/<1449175608-1146-1-git-send-email-sasha.levin@oracle.com>
	* incorrect conversion into rtc_time in rtc_time64_to_tm() - http://lkml.kernel.org/r/<1449187944-11730-1-git-send-email-sasha.levin@oracle.com>
	* unvalidated timespec in io_getevents() - http://lkml.kernel.org/r/<CACT4Y+bBxVYLQ6LtOKrKtnLthqLHcw-BMp3aqP3mjdAvr9FULQ@mail.gmail.com>
	* [NOTABUG] signed overflow in ktime_add_safe() - http://lkml.kernel.org/r/<CACT4Y+aJ4muRnWxsUe1CMnA6P8nooO33kwG-c8YZg=0Xc8rJqw@mail.gmail.com>
		

Re: [PATCH v4 0/3] UBSAN: run-time undefined behavior sanity checker

[Andrey Ryabinin]

On 12/05/2015 03:37 AM, Andrew Morton wrote:
> On Thu, 3 Dec 2015 18:50:04 +0300 Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:
> 
>> UBSAN is run-time undefined behaviour checker. It 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.
> 
> What I'd like to see in this changelog is a description of any kernel
> issues which this checker has already identified: what were they and
> what was their potential impact at runtime.
> 
> This info will help us to understand the value of the proposed feature.
> 


It's hard for me to judge about runtime impact of those bugs,
as don't know much about what that bugged code is doing.
Frankly speaking, nothing looks too scary for me, although some bugs would
be hard to find without UBSAN.


Found bugs:

	* out-of-bounds access - 97840cb67ff5 ("netfilter: nfnetlink: fix insufficient validation in nfnetlink_bind")

undefined shifts:
	* d48458d4a768 ("jbd2: use a better hash function for the revoke table")
	* 10632008b9e1 ("clockevents: Prevent shift out of bounds")
	* 'x << -1' shift in ext4 - http://lkml.kernel.org/r/<5444EF21.8020501@samsung.com>
	* undefined rol32(0) - http://lkml.kernel.org/r/<1449198241-20654-1-git-send-email-sasha.levin@oracle.com>
	* undefined dirty_ratelimit calculation - http://lkml.kernel.org/r/<566594E2.3050306@odin.com>
	* undefined roundown_pow_of_two(0) - http://lkml.kernel.org/r/<1449156616-11474-1-git-send-email-sasha.levin@oracle.com>
	* [WONTFIX] undefined shift in __bpf_prog_run - http://lkml.kernel.org/r/<CACT4Y+ZxoR3UjLgcNdUm4fECLMx2VdtfrENMtRRCdgHB2n0bJA@mail.gmail.com>
		WONTFIX here because it should be fixed in bpf program, not in kernel.

signed overflows:
	* 32a8df4e0b33f ("sched: Fix odd values in effective_load() calculations")
	* mul overflow in ntp - http://lkml.kernel.org/r/<1449175608-1146-1-git-send-email-sasha.levin@oracle.com>
	* incorrect conversion into rtc_time in rtc_time64_to_tm() - http://lkml.kernel.org/r/<1449187944-11730-1-git-send-email-sasha.levin@oracle.com>
	* unvalidated timespec in io_getevents() - http://lkml.kernel.org/r/<CACT4Y+bBxVYLQ6LtOKrKtnLthqLHcw-BMp3aqP3mjdAvr9FULQ@mail.gmail.com>
	* [NOTABUG] signed overflow in ktime_add_safe() - http://lkml.kernel.org/r/<CACT4Y+aJ4muRnWxsUe1CMnA6P8nooO33kwG-c8YZg=0Xc8rJqw@mail.gmail.com>