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From: Prasad J Pandit <address@hidden>
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 for 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 <address@hidden>
Signed-off-by: Prasad J Pandit <address@hidden>
---
hw/scsi/vmw_pvscsi.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
Update as per:
-> https://lists.gnu.org/archive/html/qemu-devel/2016-09/msg01172.html
diff --git a/hw/scsi/vmw_pvscsi.c b/hw/scsi/vmw_pvscsi.c
index 4245c15..babac5a 100644
--- a/hw/scsi/vmw_pvscsi.c
+++ b/hw/scsi/vmw_pvscsi.c
@@ -40,6 +40,8 @@
#define PVSCSI_MAX_DEVS (64)
#define PVSCSI_MSIX_NUM_VECTORS (1)
+#define PVSCSI_MAX_SG_ELEM 2048
+
#define PVSCSI_MAX_CMD_DATA_WORDS \
(sizeof(PVSCSICmdDescSetupRings)/sizeof(uint32_t))
@@ -628,17 +630,16 @@ pvscsi_queue_pending_descriptor(PVSCSIState *s, SCSIDevice **d,
static void
pvscsi_convert_sglist(PVSCSIRequest *r)
{
- int chunk_size;
+ uint32_t chunk_size, elmcnt = 0;
uint64_t data_length = r->req.dataLen;
PVSCSISGState sg = r->sg;
- while (data_length) {
- while (!sg.resid) {
+ while (data_length && elmcnt < PVSCSI_MAX_SG_ELEM) {
+ while (!sg.resid && elmcnt++ < PVSCSI_MAX_SG_ELEM) {
pvscsi_get_next_sg_elem(&sg);
trace_pvscsi_convert_sglist(r->req.context, r->sg.dataAddr,
r->sg.resid);
}
- assert(data_length > 0);
- chunk_size = MIN((unsigned) data_length, sg.resid);
+ chunk_size = MIN(data_length, sg.resid);
if (chunk_size) {
qemu_sglist_add(&r->sgl, sg.dataAddr, chunk_size);
}
--
2.5.5
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