[PATCH rdma-next 08/12] overflow.h: Add arithmetic shift helper
From: Leon Romanovsky <leon@kernel.org>
Date: 2018-06-24 08:24:29
Also in:
linux-rdma, lkml
Subsystem:
kernel hardening (not covered by other areas), the rest · Maintainers:
Kees Cook, Linus Torvalds
From: Leon Romanovsky <redacted> Add shift_overflow() helper to help driver authors to ensure that shift operand doesn't cause to overflow, which is very common pattern for RDMA drivers. Signed-off-by: Leon Romanovsky <redacted> --- include/linux/overflow.h | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+)
diff --git a/include/linux/overflow.h b/include/linux/overflow.h
index 8712ff70995f..2a3395248e94 100644
--- a/include/linux/overflow.h
+++ b/include/linux/overflow.h@@ -202,6 +202,29 @@ #endif /* COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW */ +/** + * shift_overflow() - Peform shift operation with overflow check + * @a: value to be shifted + * @b: shift operand + * + * Checks if a << b will overflow + * + * Returns: result of shift for no overflow or SIZE_MAX for overflow + */ +static inline __must_check size_t shift_overflow(size_t a, size_t b) +{ + size_t c, res; + + if (b >= sizeof(size_t) * BITS_PER_BYTE) + return SIZE_MAX; + + c = (size_t)1 << b; + if (check_mul_overflow(a, c, &res)) + return SIZE_MAX; + + return res; +} + /** * array_size() - Calculate size of 2-dimensional array. * --
2.14.4