38 lines
1.5 KiB
Diff
38 lines
1.5 KiB
Diff
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net: pcnet: add check to validate receive data size(CVE-2015-7504)
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In loopback mode, pcnet_receive routine appends CRC code to the
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receive buffer. If the data size given is same as the buffer size,
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the appended CRC code overwrites 4 bytes after s->buffer. Added a
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check to avoid that.
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---
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hw/net/pcnet.c | 10 ++++++----
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1 file changed, 6 insertions(+), 4 deletions(-)
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Index: xen-4.6.0-testing/tools/qemu-xen-dir-remote/hw/net/pcnet.c
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===================================================================
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--- xen-4.6.0-testing.orig/tools/qemu-xen-dir-remote/hw/net/pcnet.c
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+++ xen-4.6.0-testing/tools/qemu-xen-dir-remote/hw/net/pcnet.c
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@@ -1106,7 +1106,7 @@ ssize_t pcnet_receive(NetClientState *nc
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uint32_t fcs = ~0;
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uint8_t *p = src;
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- while (p != &src[size-4])
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+ while (p != &src[size])
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CRC(fcs, *p++);
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crc_err = (*(uint32_t *)p != htonl(fcs));
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}
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@@ -1255,8 +1255,10 @@ static void pcnet_transmit(PCNetState *s
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bcnt = 4096 - GET_FIELD(tmd.length, TMDL, BCNT);
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/* if multi-tmd packet outsizes s->buffer then skip it silently.
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- Note: this is not what real hw does */
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- if (s->xmit_pos + bcnt > sizeof(s->buffer)) {
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+ * Note: this is not what real hw does.
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+ * Last four bytes of s->buffer are used to store CRC FCS code.
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+ */
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+ if (s->xmit_pos + bcnt > sizeof(s->buffer) - 4) {
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s->xmit_pos = -1;
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goto txdone;
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}
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