lm4549: Fix buffer overflow

Report from smatch:
lm4549.c:234 lm4549_write_samples(14) error:
 buffer overflow 's->buffer' 1024 <= 1024

There must be enough space to add two entries starting with index
s->buffer_level, therefore the old check was wrong.

[Peter Maydell <peter.maydell@linaro.org> clarifies the nature of the
analyser warning:

I don't object to making the change to placate the analyser,
but I don't think this is actually a buffer overrun. We always
add and remove samples from the buffer two at a time, so it's
not possible to get here with s->buffer_level == BUFFER_SIZE-1
(which is the only case where the old and new conditions
give different answers).]

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
(cherry picked from commit 8139626643cbe8dc07bd9acc88057effeedf8064)

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

diff --git a/hw/lm4549.c b/hw/lm4549.c
index 80b3ec4a5d0f7577301fff44c3601c04d11b3bae..e0137d54b6df13823ea00666783a5f37ce7afb7b 100644 (file)
--- a/hw/lm4549.c
+++ b/hw/lm4549.c
@@ -224,7 +224,7 @@ uint32_t lm4549_write_samples(lm4549_state *s, uint32_t left, uint32_t right)
        This model supports 16-bit playback.
     */
 
-    if (s->buffer_level >= LM4549_BUFFER_SIZE) {
+    if (s->buffer_level > LM4549_BUFFER_SIZE - 2) {
         DPRINTF("write_sample Buffer full\n");
         return 0;
     }