afs: Fix check for NULL terminator

Add a missing check for reaching the end of the string while attempting
to split a command.

Fixes: f94f70d ("afs: Provide a way to configure address priorities")
Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=7741f872f3c53385a2e2
Signed-off-by: Leo Stone <[email protected]>
Signed-off-by: David Howells <[email protected]>
Link: https://lore.kernel.org/[email protected]
Acked-by: David Howells <[email protected]>
cc: Marc Dionne <[email protected]>
cc: [email protected]
cc: [email protected]
Signed-off-by: Christian Brauner <[email protected]>

Author: leocstone

fs/afs/addr_prefs.c

@@ -48,7 +48,7 @@ static int afs_split_string(char **pbuf, char *strv[], unsigned int maxstrv)
 		strv[count++] = p;
 
 		/* Skip over word */
-		while (!isspace(*p))
+		while (!isspace(*p) && *p)
 			p++;
 		if (!*p)
 			break;