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* [gcc(refs/vendors/redhat/heads/gcc-8-branch)] c++: Further fix for -fsanitize=vptr [PR94325]
@ 2020-09-17 17:21 Jakub Jelinek
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From: Jakub Jelinek @ 2020-09-17 17:21 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:e98b12fcc4dc2618ee7ac9298c06b67aaacf9f3c
commit e98b12fcc4dc2618ee7ac9298c06b67aaacf9f3c
Author: Jakub Jelinek <jakub@redhat.com>
Date: Wed Apr 8 15:30:16 2020 +0200
c++: Further fix for -fsanitize=vptr [PR94325]
For -fsanitize=vptr, we insert a NULL store into the vptr instead of just
adding a CLOBBER of this. build_clobber_this makes the CLOBBER conditional
on in_charge (implicit) parameter whenever CLASSTYPE_VBASECLASSES, but when
adding this conditionalization to the -fsanitize=vptr code in PR87095,
I wanted it to catch some more cases when the class has CLASSTYPE_VBASECLASSES,
but the vptr is still not shared with something else, otherwise the
sanitization would be less effective.
The following testcase shows that the chosen test that CLASSTYPE_PRIMARY_BINFO
is non-NULL and has BINFO_VIRTUAL_P set wasn't sufficient,
the D class has still sizeof(D) == sizeof(void*) and thus contains just
a single vptr, but while in B::~B() this results in the vptr not being
cleared, in C::~C() this condition isn't true, as CLASSTYPE_PRIMARY_BINFO
in that case is B and is not BINFO_VIRTUAL_P, so it clears the vptr, but the
D::~D() dtor after invoking C::~C() invokes A::~A() with an already cleared
vptr, which is then reported.
The following patch is just a shot in the dark, keep looking through
CLASSTYPE_PRIMARY_BINFO until we find BINFO_VIRTUAL_P, but it works on the
existing testcase as well as this new one.
2020-04-08 Jakub Jelinek <jakub@redhat.com>
PR c++/94325
* decl.c (begin_destructor_body): For CLASSTYPE_VBASECLASSES class
dtors, if CLASSTYPE_PRIMARY_BINFO is non-NULL, but not BINFO_VIRTUAL_P,
look at CLASSTYPE_PRIMARY_BINFO of its BINFO_TYPE if it is not
BINFO_VIRTUAL_P, and so on.
* g++.dg/ubsan/vptr-15.C: New test.
(cherry picked from commit 4cf6b06cb5b02c053738e2975e3b7a4b3c577401)
Diff:
---
gcc/cp/decl.c | 20 +++++++++++++-------
gcc/testsuite/g++.dg/ubsan/vptr-15.C | 14 ++++++++++++++
2 files changed, 27 insertions(+), 7 deletions(-)
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index f2b52fb674e..9f1444ccff6 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -15592,14 +15592,20 @@ begin_destructor_body (void)
/* If the vptr is shared with some virtual nearly empty base,
don't clear it if not in charge, the dtor of the virtual
nearly empty base will do that later. */
- if (CLASSTYPE_VBASECLASSES (current_class_type)
- && CLASSTYPE_PRIMARY_BINFO (current_class_type)
- && BINFO_VIRTUAL_P
- (CLASSTYPE_PRIMARY_BINFO (current_class_type)))
+ if (CLASSTYPE_VBASECLASSES (current_class_type))
{
- stmt = convert_to_void (stmt, ICV_STATEMENT,
- tf_warning_or_error);
- stmt = build_if_in_charge (stmt);
+ tree c = current_class_type;
+ while (CLASSTYPE_PRIMARY_BINFO (c))
+ {
+ if (BINFO_VIRTUAL_P (CLASSTYPE_PRIMARY_BINFO (c)))
+ {
+ stmt = convert_to_void (stmt, ICV_STATEMENT,
+ tf_warning_or_error);
+ stmt = build_if_in_charge (stmt);
+ break;
+ }
+ c = BINFO_TYPE (CLASSTYPE_PRIMARY_BINFO (c));
+ }
}
finish_decl_cleanup (NULL_TREE, stmt);
}
diff --git a/gcc/testsuite/g++.dg/ubsan/vptr-15.C b/gcc/testsuite/g++.dg/ubsan/vptr-15.C
new file mode 100644
index 00000000000..f6f36a58bab
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ubsan/vptr-15.C
@@ -0,0 +1,14 @@
+// PR c++/94325
+// { dg-do run { target c++11 } }
+// { dg-options "-fsanitize=vptr -fno-sanitize-recover=vptr" }
+
+struct A { virtual ~A () = default; };
+struct B : public virtual A {};
+struct C : public B {};
+struct D : public C {};
+
+int
+main ()
+{
+ D a;
+}
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