sh: Fix some arithmetic undefined behaviour.

Fix shifts of possibly negative numbers found with ubsan and avoid signed
integer overflow when hashing an extremely long command name.

MFC after:	1 week

1 files changed, 1 insertions, 1 deletions

diff --git a/bin/sh/alias.c b/bin/sh/alias.c
index 21f3f44..a77ce99 100644
--- a/bin/sh/alias.c
+++ b/bin/sh/alias.c
@@ -248,7 +248,7 @@ hashalias(const char *p)
 {
 	unsigned int hashval;
 
-	hashval = *p << 4;
+	hashval = (unsigned char)*p << 4;
 	while (*p)
 		hashval+= *p++;
 	return &atab[hashval % ATABSIZE];