Added a simple fake_sigreturn testcase which builds a ucontext_t
with a badly sized header that causes a overrun in the __reserved
area and place it onto the stack. Expects a SIGSEGV on test PASS.
Signed-off-by: Cristian Marussi <cristian.marussi@xxxxxxx>
---
.../arm64/signal/testcases/.gitignore | 1 +
.../testcases/fake_sigreturn_bad_size.c | 85 +++++++++++++++++++
2 files changed, 86 insertions(+)
create mode 100644 tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_size.c
diff --git a/tools/testing/selftests/arm64/signal/testcases/.gitignore b/tools/testing/selftests/arm64/signal/testcases/.gitignore
index 94f9baaf638c..3408e0f5ba98 100644
--- a/tools/testing/selftests/arm64/signal/testcases/.gitignore
+++ b/tools/testing/selftests/arm64/signal/testcases/.gitignore
@@ -8,3 +8,4 @@ fake_sigreturn_bad_magic
fake_sigreturn_bad_size_for_magic0
fake_sigreturn_missing_fpsimd
fake_sigreturn_duplicated_fpsimd
+fake_sigreturn_bad_size
diff --git a/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_size.c b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_size.c
new file mode 100644
index 000000000000..1467fb534d8b
--- /dev/null
+++ b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_size.c
@@ -0,0 +1,85 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2019 ARM Limited */
+
+#include <stdio.h>
+#include <ucontext.h>
+
+#include "test_signals_utils.h"
+#include "testcases.h"
+
+struct fake_sigframe sf;
+
+#define MIN_SZ_ALIGN 16
+
+static int fake_sigreturn_bad_size_run(struct tdescr *td,
+ siginfo_t *si, ucontext_t *uc)
+{
+ size_t resv_sz, need_sz, offset;
+ struct _aarch64_ctx *shead = GET_SF_RESV_HEAD(sf), *head;
+
+ /* just to fill the ucontext_t with something real */
+ if (!get_current_context(td, &sf.uc))
+ return 1;
+
+ resv_sz = GET_SF_RESV_SIZE(sf);
+ /*
+ * find the terminator, preserving existing headers
+ * and verify amount of spare room in __reserved area.
+ */
+ head = get_terminator(shead, resv_sz, &offset);
+ /*
+ * try stripping extra_context header when low on space:
+ * we need at least for the bad sized esr_context.
+ */
+ need_sz = HDR_SZ + sizeof(struct esr_context);
+ if (head && resv_sz - offset < need_sz) {
+ fprintf(stderr, "Low on space:%zd. Discarding extra_context.\n",
+ resv_sz - offset);
+ head = get_header(shead, EXTRA_MAGIC, resv_sz, &offset);
+ }
+ /* just give up and timeout if still not enough space */
+ if (head && resv_sz - offset >= need_sz) {
+ fprintf(stderr, "Mangling template header. Spare space:%zd\n",
+ resv_sz - offset);
+ /*
+ * Use an esr_context to build a fake header with a
+ * size greater then the free __reserved area minus HDR_SZ;
+ * using ESR_MAGIC here since it is not checked for size nor
+ * is limited to one instance.
+ *
+ * At first inject an additional normal esr_context
+ */
+ head->magic = ESR_MAGIC;
+ head->size = sizeof(struct esr_context);
+ /* and terminate properly */
+ write_terminator_record(GET_RESV_NEXT_HEAD(head));
+ ASSERT_GOOD_CONTEXT(&sf.uc);
+
+ /*
+ * now mess with fake esr_context size: leaving less space than
+ * neededwhile keeping size value 16-aligned
+ *
+ * It must trigger a SEGV from Kernel on:
+ *
+ * resv_sz - offset < sizeof(*head)
+ */
+ /* at first set the maximum good 16-aligned size */
+ head->size = (resv_sz - offset - need_sz + MIN_SZ_ALIGN) & ~0xfUL;
+ /* plus a bit more of 16-aligned sized stuff */
+ head->size += MIN_SZ_ALIGN;
+ /* and terminate properly */
+ write_terminator_record(GET_RESV_NEXT_HEAD(head));
+ ASSERT_BAD_CONTEXT(&sf.uc);
+ fake_sigreturn(&sf, sizeof(sf), 16);
+ }
+
+ return 1;
+}
+
+struct tdescr tde = {
+ .name = "FAKE_SIGRETURN_BAD_SIZE",
+ .descr = "Triggers a fake sigreturn with a sigframe including a badly sized header which overruns the __reserved area",
+ .sig_ok = SIGSEGV,
+ .timeout = 3,
+ .run = fake_sigreturn_bad_size_run,
+};
--
2.17.1
