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From: Prasad J Pandit <pjp@fedoraproject.org>
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Date: Tue, 6 Sep 2016 02:20:43 +0530
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Subject: [PATCH] scsi: pvscsi: limit loop to fetch SG list
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In PVSCSI paravirtual SCSI bus, pvscsi_convert_sglist can take a very
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long time or go into an infinite loop due to two different bugs:
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1) the request descriptor data length is defined to be 64 bit. While
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building SG list from a request descriptor, it gets truncated to 32bit
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in routine 'pvscsi_convert_sglist'. This could lead to an infinite loop
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situation large 'dataLen' values when data_length is cast to uint32_t and
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chunk_size becomes always zero. Fix this by removing the incorrect cast.
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2) pvscsi_get_next_sg_elem can be called arbitrarily many times if the
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element has a zero length. Get out of the loop early when this happens,
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by introducing an upper limit on the number of SG list elements.
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Reported-by: Li Qiang <liqiang6-s@360.cn>
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Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
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Message-Id: <1473108643-12983-1-git-send-email-ppandit@redhat.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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(cherry picked from commit 49adc5d3f8c6bb75e55ebfeab109c5c37dea65e8)
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---
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hw/scsi/vmw_pvscsi.c | 11 ++++++-----
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1 file changed, 6 insertions(+), 5 deletions(-)
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diff --git a/hw/scsi/vmw_pvscsi.c b/hw/scsi/vmw_pvscsi.c
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index 4245c15..babac5a 100644
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--- a/hw/scsi/vmw_pvscsi.c
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+++ b/hw/scsi/vmw_pvscsi.c
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@@ -40,6 +40,8 @@
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#define PVSCSI_MAX_DEVS (64)
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#define PVSCSI_MSIX_NUM_VECTORS (1)
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+#define PVSCSI_MAX_SG_ELEM 2048
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+
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#define PVSCSI_MAX_CMD_DATA_WORDS \
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(sizeof(PVSCSICmdDescSetupRings)/sizeof(uint32_t))
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@@ -628,17 +630,16 @@ pvscsi_queue_pending_descriptor(PVSCSIState *s, SCSIDevice **d,
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static void
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pvscsi_convert_sglist(PVSCSIRequest *r)
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{
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- int chunk_size;
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+ uint32_t chunk_size, elmcnt = 0;
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uint64_t data_length = r->req.dataLen;
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PVSCSISGState sg = r->sg;
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- while (data_length) {
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- while (!sg.resid) {
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+ while (data_length && elmcnt < PVSCSI_MAX_SG_ELEM) {
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+ while (!sg.resid && elmcnt++ < PVSCSI_MAX_SG_ELEM) {
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pvscsi_get_next_sg_elem(&sg;;
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trace_pvscsi_convert_sglist(r->req.context, r->sg.dataAddr,
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r->sg.resid);
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}
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- assert(data_length > 0);
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- chunk_size = MIN((unsigned) data_length, sg.resid);
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+ chunk_size = MIN(data_length, sg.resid);
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if (chunk_size) {
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qemu_sglist_add(&r->sgl, sg.dataAddr, chunk_size);
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}
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