qemu-char: Fix potential out of bounds access to local arrays

Latest gcc-4.8 supports a new option -fsanitize=address which activates
an AddressSanitizer. This AddressSanitizer stops the QEMU system emulation
very early because two character arrays of size 8 are potentially written
with 9 bytes.

Commit 6ea314d91439741e95772dfbab98b4135e04bebb added the code.

There is no obvious reason why width or height could need 8 characters,
so reduce it to 7 characters which together with the terminating '\0'
fit into the arrays.

Cc: qemu-stable <qemu-stable@nongnu.org>
Signed-off-by: Stefan Weil <sw@weilnetz.de>
Reviewed-by: Alex Bennée <alex@bennee.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
(cherry picked from commit 49aa4058ac6dd0081aaa45776f07c98df397ca5e)

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/qemu-char.c b/qemu-char.c
index fc1c23d2c3c3691b5cdfb1fe27602b122aee0c1b..649c9f92f2b1344fc61d368e9410ca53ecdc3956 100644 (file)
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -2969,11 +2969,11 @@ QemuOpts *qemu_chr_parse_compat(const char *label, const char *filename)
     if (strstart(filename, "vc", &p)) {
         qemu_opt_set(opts, "backend", "vc");
         if (*p == ':') {
-            if (sscanf(p+1, "%8[0-9]x%8[0-9]", width, height) == 2) {
+            if (sscanf(p+1, "%7[0-9]x%7[0-9]", width, height) == 2) {
                 /* pixels */
                 qemu_opt_set(opts, "width", width);
                 qemu_opt_set(opts, "height", height);
-            } else if (sscanf(p+1, "%8[0-9]Cx%8[0-9]C", width, height) == 2) {
+            } else if (sscanf(p+1, "%7[0-9]Cx%7[0-9]C", width, height) == 2) {
                 /* chars */
                 qemu_opt_set(opts, "cols", width);
                 qemu_opt_set(opts, "rows", height);