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From dc546cbfdefb8ddbaf121d3b075ca723df264d1c Mon Sep 17 00:00:00 2001
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From: Vlad Yasevich <vyasevic@redhat.com>
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Date: Wed, 16 Dec 2015 02:58:22 +0100
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Subject: [PATCH 5/6] rtl8139: Fix receive buffer overflow check
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Message-id: <1450234703-7606-2-git-send-email-vyasevic@redhat.com>
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Patchwork-id: 68617
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O-Subject: [RHEL7.3 qemu-kvm PATCH 1/2] rtl8139: Fix receive buffer overflow check
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Bugzilla: 1252757
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>
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RH-Acked-by: Xiao Wang <jasowang@redhat.com>
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rtl8139_do_receive() tries to check for the overflow condition
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by making sure that packet_size + 8 does not exceed the
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available buffer space. The issue here is that RxBuffAddr,
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used to calculate available buffer space, is aligned to a
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a 4 byte boundry after every update. So it is possible that
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every packet ends up being slightly padded when written
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to the receive buffer. This padding is not taken into
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account when checking for overflow and we may end up missing
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the overflow condition can causing buffer overwrite.
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This patch takes alignment into consideration when
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checking for overflow condition.
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Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
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Reviewed-by: Jason Wang <jasowang@redhat.com>
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Message-id: 1441121206-6997-2-git-send-email-vyasevic@redhat.com
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit fabdcd3392f16fc666b1d04fc1bbe5f1dbbf10a4)
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Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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hw/net/rtl8139.c | 6 ++++--
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1 file changed, 4 insertions(+), 2 deletions(-)
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diff --git a/hw/net/rtl8139.c b/hw/net/rtl8139.c
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index 4f89328..6a167df 100644
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--- a/hw/net/rtl8139.c
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+++ b/hw/net/rtl8139.c
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@@ -1137,7 +1137,9 @@ static ssize_t rtl8139_do_receive(NetClientState *nc, const uint8_t *buf, size_t
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/* if receiver buffer is empty then avail == 0 */
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- if (avail != 0 && size + 8 >= avail)
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+#define RX_ALIGN(x) (((x) + 3) & ~0x3)
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+
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+ if (avail != 0 && RX_ALIGN(size + 8) >= avail)
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{
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DPRINTF("rx overflow: rx buffer length %d head 0x%04x "
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"read 0x%04x === available 0x%04x need 0x%04x\n",
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@@ -1165,7 +1167,7 @@ static ssize_t rtl8139_do_receive(NetClientState *nc, const uint8_t *buf, size_t
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rtl8139_write_buffer(s, (uint8_t *)&val, 4);
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/* correct buffer write pointer */
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- s->RxBufAddr = MOD2((s->RxBufAddr + 3) & ~0x3, s->RxBufferSize);
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+ s->RxBufAddr = MOD2(RX_ALIGN(s->RxBufAddr), s->RxBufferSize);
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/* now we can signal we have received something */
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--
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1.8.3.1
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