pcnet: force the buffer access to be in bounds during tx

4096 is the maximum length per TMD and it is also currently the size of
the relay buffer pcnet driver uses for sending the packet data to QEMU
for further processing. With packet spanning multiple TMDs it can
happen that the overall packet size will be bigger than sizeof(buffer),
which results in memory corruption.

Fix this by only allowing to queue maximum sizeof(buffer) bytes.

This is CVE-2015-3209.

[Fixed 3-space indentation to QEMU's 4-space coding standard.
--Stefan]

Signed-off-by: Petr Matousek <pmatouse@redhat.com>
Reported-by: Matt Tait <matttait@google.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Petr Matousek 2015-05-24 10:53:44 +02:00 committed by Stefan Hajnoczi
parent b0411142f4
commit 9f7c594c00
1 changed files with 8 additions and 0 deletions

View File

@ -1241,6 +1241,14 @@ static void pcnet_transmit(PCNetState *s)
}
bcnt = 4096 - GET_FIELD(tmd.length, TMDL, BCNT);
/* if multi-tmd packet outsizes s->buffer then skip it silently.
Note: this is not what real hw does */
if (s->xmit_pos + bcnt > sizeof(s->buffer)) {
s->xmit_pos = -1;
goto txdone;
}
s->phys_mem_read(s->dma_opaque, PHYSADDR(s, tmd.tbadr),
s->buffer + s->xmit_pos, bcnt, CSR_BSWP(s));
s->xmit_pos += bcnt;