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

2 files changed, 3 insertions, 4 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];
diff --git a/bin/sh/exec.c b/bin/sh/exec.c
index c9d4126..7d18c3c 100644
--- a/bin/sh/exec.c
+++ b/bin/sh/exec.c
@@ -522,17 +522,16 @@ static struct tblentry **lastcmdentry;
 static struct tblentry *
 cmdlookup(const char *name, int add)
 {
-	int hashval;
+	unsigned int hashval;
 	const char *p;
 	struct tblentry *cmdp;
 	struct tblentry **pp;
 	size_t len;
 
 	p = name;
-	hashval = *p << 4;
+	hashval = (unsigned char)*p << 4;
 	while (*p)
 		hashval += *p++;
-	hashval &= 0x7FFF;
 	pp = &cmdtable[hashval % CMDTABLESIZE];
 	for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
 		if (equal(cmdp->cmdname, name))