[PATCH 10/20] target: Avoid signed overflow in bit and byte conversion helpers

[Bart Van Assche <bvanassche@acm.org>]

Cast bits to unsigned int before adding bits_in_char - 1 in
bits_to_bytes(), and widen bytes_to_bits() to accept and return long while
performing the multiplication by bits_in_char in unsigned long.

Prevent signed integer addition overflow in bits_to_bytes() near INT_MAX
and prevent 32-bit signed multiplication overflow and truncation in
bytes_to_bits() on large array offsets and sparse initializers.

Fixes: eb800bdc3791 ("Unhardcode byte size being 8 bits.")
Fixes: b3e9d87c6a98 ("sparse: make bits_to_bytes round up instead of down")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 target.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/target.h b/target.h
index 92b8af9169d7..0b21702c45f1 100644
--- a/target.h
+++ b/target.h
@@ -143,12 +143,12 @@ void target_init(void);
 
 static inline int bits_to_bytes(int bits)
 {
-	return bits >= 0 ? (bits + bits_in_char - 1) / bits_in_char : -1;
+	return bits >= 0 ? ((unsigned int)bits + bits_in_char - 1) / bits_in_char : -1;
 }
 
-static inline int bytes_to_bits(int bytes)
+static inline long bytes_to_bits(long bytes)
 {
-	return bytes * bits_in_char;
+	return (unsigned long)bytes * bits_in_char;
 }
 
 static inline unsigned long array_element_offset(unsigned long base_bits, int idx)