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
--