hw/block/onenand: Fix off-by-one error allowing out-of-bounds read

An off-by-one error in a switch case in onenand_read() allowed
a misbehaving guest to read off the end of a block of memory.

NB: the onenand device is used only by the "n800" and "n810"
machines, which are usable only with TCG, not KVM, so this is
not a security issue.
Reported-by: NThomas Huth <thuth@redhat.com>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Message-id: 20181115143535.5885-2-peter.maydell@linaro.org
Suggested-by: NRichard Henderson <richard.henderson@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/block/onenand.c

@@ -608,7 +608,7 @@ static uint64_t onenand_read(void *opaque, hwaddr addr,
     int offset = addr >> s->shift;
 
     switch (offset) {
-    case 0x0000 ... 0xc000:
+    case 0x0000 ... 0xbffe:
         return lduw_le_p(s->boot[0] + addr);
 
     case 0xf000:	/* Manufacturer ID */