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------------------------------------------------------------------------
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*From*: P J P
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*Subject*: [Qemu-devel] [PATCH 2/2] scsi: check dma length before
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reading scsi command(CVE-2016-4441)
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*Date*: Thu, 19 May 2016 16:09:31 +0530
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------------------------------------------------------------------------
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From: Prasad J Pandit <address@hidden>
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The 53C9X Fast SCSI Controller(FSC) comes with an internal 16-byte
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FIFO buffer. It is used to handle command and data transfer.
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Routine get_cmd() uses DMA to read scsi commands into this buffer.
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Add check to validate DMA length against buffer size to avoid any
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overrun.
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Fixes CVE-2016-4441
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Reported-by: Li Qiang <address@hidden>
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Signed-off-by: Prasad J Pandit <address@hidden>
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---
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hw/scsi/esp.c | 11 +++++++----
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1 file changed, 7 insertions(+), 4 deletions(-)
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diff --git a/tools/qemu-xen-traditional/hw/esp.c b/tools/qemu-xen-traditional/hw/esp.c
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index 01497e6..591c817 100644
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--- a/tools/qemu-xen-traditional/hw/esp.c
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+++ b/tools/qemu-xen-traditional/hw/esp.c
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@@ -82,7 +82,7 @@ void esp_request_cancelled(SCSIRequest *req)
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}
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}
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-static uint32_t get_cmd(ESPState *s, uint8_t *buf)
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+static uint32_t get_cmd(ESPState *s, uint8_t *buf, uint8_t buflen)
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{
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uint32_t dmalen;
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int target;
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@@ -92,6 +92,9 @@ static uint32_t get_cmd(ESPState *s, uint8_t *buf)
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target = s->wregs[ESP_WBUSID] & BUSID_DID;
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if (s->dma) {
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dmalen = s->rregs[ESP_TCLO] | (s->rregs[ESP_TCMID] << 8);
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+ if (dmalen > buflen) {
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+ return 0;
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+ }
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s->dma_memory_read(s->dma_opaque, buf, dmalen);
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} else {
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dmalen = s->ti_size;
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@@ -166,7 +169,7 @@ static void handle_satn(ESPState *s)
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uint8_t buf[32];
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int len;
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- len = get_cmd(s, buf);
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+ len = get_cmd(s, buf, sizeof(buf));
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if (len)
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do_cmd(s, buf);
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}
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@@ -192,7 +195,7 @@ static void handle_satn_stop(ESPState *s)
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static void handle_satn_stop(ESPState *s)
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{
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- s->cmdlen = get_cmd(s, s->cmdbuf);
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+ s->cmdlen = get_cmd(s, s->cmdbuf, sizeof(s->cmdbuf));
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if (s->cmdlen) {
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DPRINTF("Set ATN & Stop: cmdlen %d\n", s->cmdlen);
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s->do_cmd = 1;
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--
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2.5.5
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