[PATCH] arm: ubsan: select ARCH_HAS_UBSAN_SANITIZE_ALL

[PATCH] arm: ubsan: select ARCH_HAS_UBSAN_SANITIZE_ALL

[Seung-Woo Kim]

To enable UBSAN on arm, this patch enables ARCH_HAS_UBSAN_SANITIZE_ALL
from arm confiuration. Basic kernel bootup test is passed on arm with
CONFIG_UBSAN_SANITIZE_ALL enabled.

Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
---
This is resend of the patch I already sent, [1], without RFC tag.
[1] https://patchwork.kernel.org/patch/9189533/

I tested kernel build and basic boot up on Exynos5422, Exynos4412 and
Exynos3250 SoC boards.

At previous time on [1], there were some build error on other systems,
but they were caused by driver bug or gcc bug. So I think UBSAN on ARM
can be re-considered.
---
 arch/arm/Kconfig                  |    1 +
 arch/arm/boot/compressed/Makefile |    1 +
 arch/arm/vdso/Makefile            |    1 +
 3 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index a9c4e48..a80f9b1 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -7,6 +7,7 @@ config ARM
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_HAVE_CUSTOM_GPIO_H
 	select ARCH_HAS_GCOV_PROFILE_ALL
+	select ARCH_HAS_UBSAN_SANITIZE_ALL
 	select ARCH_MIGHT_HAVE_PC_PARPORT
 	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_USE_BUILTIN_BSWAP
diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index d50430c..883374f 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -23,6 +23,7 @@ OBJS		+= hyp-stub.o
 endif
 
 GCOV_PROFILE		:= n
+UBSAN_SANITIZE		:= n
 
 #
 # Architecture dependencies
diff --git a/arch/arm/vdso/Makefile b/arch/arm/vdso/Makefile
index 59a8fa7..cb90e59 100644
--- a/arch/arm/vdso/Makefile
+++ b/arch/arm/vdso/Makefile
@@ -28,6 +28,7 @@ CFLAGS_vgettimeofday.o = -O2
 
 # Disable gcov profiling for VDSO code
 GCOV_PROFILE := n
+UBSAN_SANITIZE := n
 
 # Force dependency
 $(obj)/vdso.o : $(obj)/vdso.so
-- 
1.7.4.1

UBSAN: Undefined behaviour in ./arch/arm/include/asm/bitops.h

[Seung-Woo Kim]

With the patch "arm: ubsan: select ARCH_HAS_UBSAN_SANITIZE_ALL", I got
following UBSAN warning on Exynos5422 SoC board.


================================================================================
UBSAN: Undefined behaviour in ./arch/arm/include/asm/bitops.h:296:17
negation of -2147483648 cannot be represented in type 'int':
CPU: 2 PID: 5637 Comm: fsck.ext4 Tainted: G        W
4.8.0-rc7-00173-g142932f #25
Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[<c0119e28>] (unwind_backtrace) from [<c01123dc>] (show_stack+0x20/0x24)
[<c01123dc>] (show_stack) from [<c0617f70>] (dump_stack+0x84/0xa0)
[<c0617f70>] (dump_stack) from [<c0672ba0>] (ubsan_epilogue+0x14/0x50)
[<c0672ba0>] (ubsan_epilogue) from [<c067335c>]
(__ubsan_handle_negate_overflow+0x68/0x6c)
[<c067335c>] (__ubsan_handle_negate_overflow) from [<c0621044>]
(radix_tree_next_chunk+0x4e8/0x5ac)
[<c0621044>] (radix_tree_next_chunk) from [<c0286abc>]
(find_get_pages_tag+0x1b0/0x390)
[<c0286abc>] (find_get_pages_tag) from [<c02a6154>]
(pagevec_lookup_tag+0x38/0x68)
[<c02a6154>] (pagevec_lookup_tag) from [<c029e818>]
(write_cache_pages+0x134/0x85c)
[<c029e818>] (write_cache_pages) from [<c029ef9c>]
(generic_writepages+0x5c/0x9c)
[<c029ef9c>] (generic_writepages) from [<c038eae8>]
(blkdev_writepages+0x18/0x1c)
[<c038eae8>] (blkdev_writepages) from [<c02a2054>] (do_writepages+0x58/0xa4)
[<c02a2054>] (do_writepages) from [<c0289abc>]
(__filemap_fdatawrite_range+0xac/0x10c)
[<c0289abc>] (__filemap_fdatawrite_range) from [<c0289cc8>]
(filemap_write_and_wait_range+0x54/0xb8)
[<c0289cc8>] (filemap_write_and_wait_range) from [<c038f75c>]
(blkdev_fsync+0x40/0xa4)
[<c038f75c>] (blkdev_fsync) from [<c0381bf0>] (vfs_fsync_range+0x70/0x160)
[<c0381bf0>] (vfs_fsync_range) from [<c0381d68>] (do_fsync+0x4c/0x74)
[<c0381d68>] (do_fsync) from [<c038224c>] (SyS_fsync+0x1c/0x20)
[<c038224c>] (SyS_fsync) from [<c010bd20>] (ret_fast_syscall+0x0/0x3c)
================================================================================

================================================================================
UBSAN: Undefined behaviour in ./arch/arm/include/asm/bitops.h:296:17
negation of -2147483648 cannot be represented in type 'int':
CPU: 3 PID: 6313 Comm: enlightenment Tainted: G        W
4.8.0-rc7-00173-g142932f #25
Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[<c0119e28>] (unwind_backtrace) from [<c01123dc>] (show_stack+0x20/0x24)
[<c01123dc>] (show_stack) from [<c0617f10>] (dump_stack+0x84/0xa0)
[<c0617f10>] (dump_stack) from [<c0672b40>] (ubsan_epilogue+0x14/0x50)
[<c0672b40>] (ubsan_epilogue) from [<c06732fc>]
(__ubsan_handle_negate_overflow+0x68/0x6c)
[<c06732fc>] (__ubsan_handle_negate_overflow) from [<c0147f54>]
(next_signal+0x114/0x16c)
[<c0147f54>] (next_signal) from [<c0147fdc>] (dequeue_signal+0x30/0x30c)
[<c0147fdc>] (dequeue_signal) from [<c014cb58>] (get_signal+0x120/0xe84)
[<c014cb58>] (get_signal) from [<c01114fc>] (do_signal+0x37c/0x550)
[<c01114fc>] (do_signal) from [<c01119b8>] (do_work_pending+0xd0/0x134)
[<c01119b8>] (do_work_pending) from [<c010bd74>]
(slow_work_pending+0xc/0x20)
================================================================================

Regards,
- Seung-Woo Kim

-- 
Seung-Woo Kim
Samsung Software R&D Center
--

Re: UBSAN: Undefined behaviour in ./arch/arm/include/asm/bitops.h

[Russell King - ARM Linux]

On Sat, Sep 24, 2016 at 01:45:33PM +0900, Seung-Woo Kim wrote:
> With the patch "arm: ubsan: select ARCH_HAS_UBSAN_SANITIZE_ALL", I got
> following UBSAN warning on Exynos5422 SoC board.

Well, the simple solution is to have fls() and ffs() take unsigned int
arguments rather than ints - but the question that brings up is: why
do both of these take signed ints?  It seems at least to me that it
would be more sensible for these to take unsigned int, or even
unsigned long like the other bitops do.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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