parsers: fix buffer overflow by invalid parent revision read from revlog
If revlog file is corrupted, it can have parent pointing to invalid revision.
So we should validate it before updating nothead[], phases[], seen[], etc.
Otherwise it would cause segfault at best.
We could use "rev" instead of "maxrev" as upper bound, but I think the explicit
"maxrev" can clarify that we just want to avoid possible buffer overflow
vulnerability.
--- a/mercurial/parsers.c Thu Jul 16 11:12:15 2015 -0700
+++ b/mercurial/parsers.c Thu Jul 16 23:36:08 2015 +0900
@@ -752,8 +752,8 @@
return PyString_AS_STRING(self->data) + pos * v1_hdrsize;
}
-static inline void index_get_parents(indexObject *self, Py_ssize_t rev,
- int *ps)
+static inline int index_get_parents(indexObject *self, Py_ssize_t rev,
+ int *ps, int maxrev)
{
if (rev >= self->length - 1) {
PyObject *tuple = PyList_GET_ITEM(self->added,
@@ -765,6 +765,13 @@
ps[0] = getbe32(data + 24);
ps[1] = getbe32(data + 28);
}
+ /* If index file is corrupted, ps[] may point to invalid revisions. So
+ * there is a risk of buffer overflow to trust them unconditionally. */
+ if (ps[0] > maxrev || ps[1] > maxrev) {
+ PyErr_SetString(PyExc_ValueError, "parent out of range");
+ return -1;
+ }
+ return 0;
}
@@ -1149,7 +1156,8 @@
if (minrevallphases != -1) {
int parents[2];
for (i = minrevallphases; i < len; i++) {
- index_get_parents(self, i, parents);
+ if (index_get_parents(self, i, parents, len - 1) < 0)
+ goto release_phasesetlist;
set_phase_from_parents(phases, parents[0], parents[1], i);
}
}
@@ -1248,7 +1256,8 @@
continue;
}
- index_get_parents(self, i, parents);
+ if (index_get_parents(self, i, parents, len - 1) < 0)
+ goto bail;
for (j = 0; j < 2; j++) {
if (parents[j] >= 0)
nothead[parents[j]] = 1;
@@ -1716,7 +1725,8 @@
}
}
}
- index_get_parents(self, v, parents);
+ if (index_get_parents(self, v, parents, maxrev) < 0)
+ goto bail;
for (i = 0; i < 2; i++) {
int p = parents[i];
@@ -1813,7 +1823,8 @@
continue;
sv = seen[v];
- index_get_parents(self, v, parents);
+ if (index_get_parents(self, v, parents, maxrev) < 0)
+ goto bail;
for (i = 0; i < 2; i++) {
int p = parents[i];
--- a/tests/test-parseindex.t Thu Jul 16 11:12:15 2015 -0700
+++ b/tests/test-parseindex.t Thu Jul 16 23:36:08 2015 +0900
@@ -59,3 +59,62 @@
26333235a41c
$ cd ..
+
+Test corrupted p1/p2 fields that could cause SEGV at parsers.c:
+
+ $ mkdir invalidparent
+ $ cd invalidparent
+
+ $ hg clone --pull -q --config phases.publish=False ../a limit
+ $ hg clone --pull -q --config phases.publish=False ../a segv
+ $ rm -R limit/.hg/cache segv/.hg/cache
+
+ $ python <<EOF
+ > data = open("limit/.hg/store/00changelog.i", "rb").read()
+ > for n, p in [('limit', '\0\0\0\x02'), ('segv', '\0\x01\0\0')]:
+ > # corrupt p1 at rev0 and p2 at rev1
+ > d = data[:24] + p + data[28:127 + 28] + p + data[127 + 32:]
+ > open(n + "/.hg/store/00changelog.i", "wb").write(d)
+ > EOF
+
+ $ hg debugindex -f1 limit/.hg/store/00changelog.i
+ rev flag offset length size base link p1 p2 nodeid
+ 0 0000 0 63 62 0 0 2 -1 7c31755bf9b5
+ 1 0000 63 66 65 1 1 0 2 26333235a41c
+ $ hg debugindex -f1 segv/.hg/store/00changelog.i
+ rev flag offset length size base link p1 p2 nodeid
+ 0 0000 0 63 62 0 0 65536 -1 7c31755bf9b5
+ 1 0000 63 66 65 1 1 0 65536 26333235a41c
+
+ $ cat <<EOF > test.py
+ > import sys
+ > from mercurial import changelog, scmutil
+ > cl = changelog.changelog(scmutil.vfs(sys.argv[1]))
+ > n0, n1 = cl.node(0), cl.node(1)
+ > ops = [
+ > ('compute_phases_map_sets', lambda: cl.computephases([[0], []])),
+ > ('index_headrevs', lambda: cl.headrevs()),
+ > ('find_gca_candidates', lambda: cl.commonancestorsheads(n0, n1)),
+ > ('find_deepest', lambda: cl.ancestor(n0, n1)),
+ > ]
+ > for l, f in ops:
+ > print l + ':',
+ > try:
+ > f()
+ > print 'uncaught buffer overflow?'
+ > except ValueError, inst:
+ > print inst
+ > EOF
+
+ $ python test.py limit/.hg/store
+ compute_phases_map_sets: parent out of range
+ index_headrevs: parent out of range
+ find_gca_candidates: parent out of range
+ find_deepest: parent out of range
+ $ python test.py segv/.hg/store
+ compute_phases_map_sets: parent out of range
+ index_headrevs: parent out of range
+ find_gca_candidates: parent out of range
+ find_deepest: parent out of range
+
+ $ cd ..