[Xen-changelog] [xen-unstable] [QEMU] fdc: Limit sector size to 16K

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kfraser@xxxxxxxxxxxxxxxxxxxxx
# Node ID f711b87ba951e608287abd0de028c6f0d83400a9
# Parent  f3ee62b7fb5299c89d442845e0883bcfab78c067
[QEMU] fdc: Limit sector size to 16K

In fdctrl_start_transfer the sector size field (fifo[5]) is not
checked for overflows.  This allows an arbitrarily large sector size
to be used, which can in turn result in a negative data_len field that
is then used for DMA transfers.

This can lead to the corrpuption of qemu state because some subsequent
checks on the transfer length is conducted using signed integers.

This patch limits the value fifo[5] to 7 which is the standard limit
on floppy sector size.

Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
---
 tools/ioemu/hw/fdc.c |    2 +-
 1 files changed, 1 insertion(+), 1 deletion(-)

diff -r f3ee62b7fb52 -r f711b87ba951 tools/ioemu/hw/fdc.c
--- a/tools/ioemu/hw/fdc.c      Mon Nov 27 10:08:12 2006 +0000
+++ b/tools/ioemu/hw/fdc.c      Mon Nov 27 10:09:19 2006 +0000
@@ -898,7 +898,7 @@ static void fdctrl_start_transfer (fdctr
         fdctrl->data_len = fdctrl->fifo[8];
     } else {
        int tmp;
-        fdctrl->data_len = 128 << fdctrl->fifo[5];
+        fdctrl->data_len = 128 << (fdctrl->fifo[5] > 7 ? 7 : fdctrl->fifo[5]);
         tmp = (cur_drv->last_sect - ks + 1);
         if (fdctrl->fifo[0] & 0x80)
             tmp += cur_drv->last_sect;

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