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In PVSCSI paravirtual SCSI bus, pvscsi_convert_sglist can take a very long time or go into an infinite loop due to two different bugs: 1) the request descriptor data length is defined to be 64 bit. While building SG list from a request descriptor, it gets truncated to 32bit in routine 'pvscsi_convert_sglist'. This could lead to an infinite loop situation large 'dataLen' values when data_length is cast to uint32_t and chunk_size becomes always zero. Fix this by removing the incorrect cast. 2) pvscsi_get_next_sg_elem can be called arbitrarily many times if the element has a zero length. Get out of the loop early when this happens, by introducing an upper limit on the number of SG list elements. Reported-by: Li Qiang <liqiang6-s@360.cn> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org> Message-Id: <1473108643-12983-1-git-send-email-ppandit@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>