qemu/0007-megasas-do-not-read-iovec-count-more-than-once-from-.patch

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From: Paolo Bonzini <pbonzini@redhat.com>
Date: Thu, 1 Jun 2017 17:18:57 +0200
Subject: [PATCH] megasas: do not read iovec count more than once from frame
Avoid TOC-TOU bugs depending on how the compiler behaves.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 24c0c77af515acbf0f9705e8096f33ef24d37430)
---
hw/scsi/megasas.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/hw/scsi/megasas.c b/hw/scsi/megasas.c
index 1888118e5f..c353118882 100644
--- a/hw/scsi/megasas.c
+++ b/hw/scsi/megasas.c
@@ -675,15 +675,16 @@ out:
static int megasas_map_dcmd(MegasasState *s, MegasasCmd *cmd)
{
dma_addr_t iov_pa, iov_size;
+ int iov_count;
cmd->flags = le16_to_cpu(cmd->frame->header.flags);
- if (!cmd->frame->header.sge_count) {
+ iov_count = cmd->frame->header.sge_count;
+ if (!iov_count) {
trace_megasas_dcmd_zero_sge(cmd->index);
cmd->iov_size = 0;
return 0;
- } else if (cmd->frame->header.sge_count > 1) {
- trace_megasas_dcmd_invalid_sge(cmd->index,
- cmd->frame->header.sge_count);
+ } else if (iov_count > 1) {
+ trace_megasas_dcmd_invalid_sge(cmd->index, iov_count);
cmd->iov_size = 0;
return -EINVAL;
}