https://gcc.gnu.org/g:e9c984b8d3f63a929c4a2c8d8af3732efdc9fc4c
commit r12-11188-ge9c984b8d3f63a929c4a2c8d8af3732efdc9fc4c
Author: Jakub Jelinek <ja...@redhat.com>
Date: Tue Feb 6 13:00:04 2024 +0100
asan: Don't fold some strlens with -fsanitize=address [PR110676]
The UB on the following testcase isn't diagnosed by -fsanitize=address,
because we see that the array has a single element and optimize the
strlen to 0. I think it is fine to assume e.g. for range purposes the
lower bound for the strlen as long as we don't try to optimize
strlen (str)
where we know that it returns [26, 42] to
26 + strlen (str + 26), but for the upper bound we really want to punt
on optimizing that for -fsanitize=address to read all the bytes of the
string and diagnose if we run to object end etc.
2024-02-06 Jakub Jelinek <ja...@redhat.com>
PR sanitizer/110676
* gimple-fold.cc (gimple_fold_builtin_strlen): For
-fsanitize=address
reset maxlen to sizetype maximum.
* gcc.dg/asan/pr110676.c: New test.
(cherry picked from commit d3eac7d96de790df51859f63c13838f153b416de)
Diff:
---
gcc/gimple-fold.cc | 5 +++++
gcc/testsuite/gcc.dg/asan/pr110676.c | 14 ++++++++++++++
2 files changed, 19 insertions(+)
diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
index 2381b0c23127..b8ce943fcef9 100644
--- a/gcc/gimple-fold.cc
+++ b/gcc/gimple-fold.cc
@@ -4022,6 +4022,11 @@ gimple_fold_builtin_strlen (gimple_stmt_iterator *gsi)
maxlen = wi::to_wide (max_object_size (), prec) - 2;
}
+ /* For -fsanitize=address, don't optimize the upper bound of the
+ length to be able to diagnose UB on non-zero terminated arrays. */
+ if (sanitize_flags_p (SANITIZE_ADDRESS))
+ maxlen = wi::max_value (TYPE_PRECISION (sizetype), UNSIGNED);
+
if (minlen == maxlen)
{
/* Fold the strlen call to a constant. */
diff --git a/gcc/testsuite/gcc.dg/asan/pr110676.c
b/gcc/testsuite/gcc.dg/asan/pr110676.c
new file mode 100644
index 000000000000..0ae6fdd67b59
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/asan/pr110676.c
@@ -0,0 +1,14 @@
+/* PR sanitizer/110676 */
+/* { dg-do run } */
+/* { dg-skip-if "" { *-*-* } { "*" } { "-O0" } } */
+/* { dg-shouldfail "asan" } */
+
+int
+main ()
+{
+ char s[1] = "A";
+ return __builtin_strlen (s);
+}
+
+/* { dg-output "ERROR: AddressSanitizer: stack-buffer-overflow on
address.*(\n|\r\n|\r)" } */
+/* { dg-output "READ of size.*" } */
