[Xen-changelog] [qemu-xen master] xen: fix ioreq handling

[patchbot@xxxxxxx]

commit b85f9dfdb156ae2a2a52f39a36e9f1f270614cd2
Author:     Jan Beulich <JBeulich@xxxxxxxx>
AuthorDate: Tue Nov 22 05:56:51 2016 -0700
Commit:     Stefano Stabellini <sstabellini@xxxxxxxxxx>
CommitDate: Tue Nov 22 10:29:22 2016 -0800

    xen: fix ioreq handling
    
    Avoid double fetches and bounds check size to avoid overflowing
    internal variables.
    
    This is CVE-2016-9381 / XSA-197.
    
    Reported-by: yanghongke <yanghongke@xxxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
    Signed-off-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 xen-hvm.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/xen-hvm.c b/xen-hvm.c
index 150c7e7..99b8ee8 100644
--- a/xen-hvm.c
+++ b/xen-hvm.c
@@ -810,6 +810,10 @@ static void cpu_ioreq_pio(ioreq_t *req)
     trace_cpu_ioreq_pio(req, req->dir, req->df, req->data_is_ptr, req->addr,
                          req->data, req->count, req->size);
 
+    if (req->size > sizeof(uint32_t)) {
+        hw_error("PIO: bad size (%u)", req->size);
+    }
+
     if (req->dir == IOREQ_READ) {
         if (!req->data_is_ptr) {
             req->data = do_inp(req->addr, req->size);
@@ -846,6 +850,10 @@ static void cpu_ioreq_move(ioreq_t *req)
     trace_cpu_ioreq_move(req, req->dir, req->df, req->data_is_ptr, req->addr,
                          req->data, req->count, req->size);
 
+    if (req->size > sizeof(req->data)) {
+        hw_error("MMIO: bad size (%u)", req->size);
+    }
+
     if (!req->data_is_ptr) {
         if (req->dir == IOREQ_READ) {
             for (i = 0; i < req->count; i++) {
@@ -1010,11 +1018,13 @@ static int handle_buffered_iopage(XenIOState *state)
         req.df = 1;
         req.type = buf_req->type;
         req.data_is_ptr = 0;
+        xen_rmb();
         qw = (req.size == 8);
         if (qw) {
             buf_req = &buf_page->buf_ioreq[(rdptr + 1) %
                                            IOREQ_BUFFER_SLOT_NUM];
             req.data |= ((uint64_t)buf_req->data) << 32;
+            xen_rmb();
         }
 
         handle_ioreq(state, &req);
@@ -1045,7 +1055,11 @@ static void cpu_handle_ioreq(void *opaque)
 
     handle_buffered_iopage(state);
     if (req) {
-        handle_ioreq(state, req);
+        ioreq_t copy = *req;
+
+        xen_rmb();
+        handle_ioreq(state, &copy);
+        req->data = copy.data;
 
         if (req->state != STATE_IOREQ_INPROCESS) {
             fprintf(stderr, "Badness in I/O request ... not in service?!: "
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#master

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