[libvirt] [PATCH 1/3] virbitmap: Refactor virBitmapParse to avoid access beyond bounds of array

[Peter Krempa]

The virBitmapParse function was calling virBitmapIsSet() function that
requires the caller to check the bounds of the bitmap without checking
them. This resulted into crashes when parsing a bitmap string that was
exceeding the bounds used as argument.

This patch refactors the function to use virBitmapSetBit without
checking if the bit is set (this function does the checks internally)
and then counts the bits in the bitmap afterwards (instead of keeping
track while parsing the string).

This patch also changes the "parse_error" label to a more common
"error".

The refactor should also get rid of the need to call sa_assert on the
returned variable as the callpath should allow coverity to infer the
possible return values.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=997367

Thanks to Alex Jia for tracking down the issue.
---
 src/util/virbitmap.c | 38 +++++++++++++++-----------------------
 1 file changed, 15 insertions(+), 23 deletions(-)

diff --git a/src/util/virbitmap.c b/src/util/virbitmap.c
index 7e1cd02..47c678e 100644
--- a/src/util/virbitmap.c
+++ b/src/util/virbitmap.c
@@ -297,7 +297,6 @@ virBitmapParse(const char *str,
                virBitmapPtr *bitmap,
                size_t bitmapSize)
 {
-    int ret = 0;
     bool neg = false;
     const char *cur;
     char *tmp;
@@ -330,12 +329,12 @@ virBitmapParse(const char *str,
         }

         if (!c_isdigit(*cur))
-            goto parse_error;
+            goto error;

         if (virStrToLong_i(cur, &tmp, 10, &start) < 0)
-            goto parse_error;
+            goto error;
         if (start < 0)
-            goto parse_error;
+            goto error;

         cur = tmp;

@@ -343,35 +342,29 @@ virBitmapParse(const char *str,

         if (*cur == ',' || *cur == 0 || *cur == terminator) {
             if (neg) {
-                if (virBitmapIsSet(*bitmap, start)) {
-                    ignore_value(virBitmapClearBit(*bitmap, start));
-                    ret--;
-                }
+                if (virBitmapClearBit(*bitmap, start) < 0)
+                    goto error;
             } else {
-                if (!virBitmapIsSet(*bitmap, start)) {
-                    ignore_value(virBitmapSetBit(*bitmap, start));
-                    ret++;
-                }
+                if (virBitmapSetBit(*bitmap, start) < 0)
+                    goto error;
             }
         } else if (*cur == '-') {
             if (neg)
-                goto parse_error;
+                goto error;

             cur++;
             virSkipSpaces(&cur);

             if (virStrToLong_i(cur, &tmp, 10, &last) < 0)
-                goto parse_error;
+                goto error;
             if (last < start)
-                goto parse_error;
+                goto error;

             cur = tmp;

             for (i = start; i <= last; i++) {
-                if (!virBitmapIsSet(*bitmap, i)) {
-                    ignore_value(virBitmapSetBit(*bitmap, i));
-                    ret++;
-                }
+                if (virBitmapSetBit(*bitmap, i) < 0)
+                    goto error;
             }

             virSkipSpaces(&cur);
@@ -384,14 +377,13 @@ virBitmapParse(const char *str,
         } else if (*cur == 0 || *cur == terminator) {
             break;
         } else {
-            goto parse_error;
+            goto error;
         }
     }

-    sa_assert(ret >= 0);
-    return ret;
+    return virBitmapCountBits(*bitmap);

-parse_error:
+error:
     virBitmapFree(*bitmap);
     *bitmap = NULL;
     return -1;
-- 
1.8.3.2