diff options
author | Hans de Goede <hdegoede@redhat.com> | 2013-03-28 19:17:18 +0100 |
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committer | Hans de Goede <hdegoede@redhat.com> | 2013-03-28 19:17:18 +0100 |
commit | 962bee79ffd1e3cda5501d5c5836619bb8843b47 (patch) | |
tree | 523480299dbc91be438331d19534917efb60f467 | |
parent | c602a2b93808f38200097d1fa10a63450687fa69 (diff) |
spice-qemu-char: vmc_write: Don't write more bytes then we're asked tooqemu-1.3-usbredir-wip
This one took me eons to debug, but I've finally found it now, oh well.
The usage of the MIN macro in this line:
last_out = MIN(len, qemu_chr_be_can_write(scd->chr));
Causes qemu_chr_be_can_write to be called *twice*, since the MIN macro
evaluates its arguments twice (bad MIN macro, bad!). And the result of
the call can change between the 2 calls since the guest may have consumed
some data from the virtio ringbuffer between the calls!
When this happens it is possible for qemu_chr_be_can_write to return less
then len in the call made for the comparision, and then to return more then
len in the actual call for the return-value of MIN, after which we will end
up writing len data + some extra garbage, not good.
This patch fixes this by only calling qemu_chr_be_can_write once.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
-rw-r--r-- | spice-qemu-char.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/spice-qemu-char.c b/spice-qemu-char.c index fdcac8f07..dfccca94c 100644 --- a/spice-qemu-char.c +++ b/spice-qemu-char.c @@ -40,7 +40,8 @@ static int vmc_write(SpiceCharDeviceInstance *sin, const uint8_t *buf, int len) uint8_t* p = (uint8_t*)buf; while (len > 0) { - last_out = MIN(len, qemu_chr_be_can_write(scd->chr)); + int can_write = qemu_chr_be_can_write(scd->chr); + last_out = MIN(len, can_write); if (last_out <= 0) { break; } |