Three testcases to make sure that stack reads from uninitialized
locations are accepted by verifier when executed in privileged mode:
- read from a fixed offset;
- read from a variable offset;
- passing a pointer to stack to a helper converts
STACK_INVALID to STACK_MISC.
Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
.../selftests/bpf/prog_tests/uninit_stack.c | 9 ++
.../selftests/bpf/progs/uninit_stack.c | 87 +++++++++++++++++++
2 files changed, 96 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/uninit_stack.c
create mode 100644 tools/testing/selftests/bpf/progs/uninit_stack.c
diff --git a/tools/testing/selftests/bpf/prog_tests/uninit_stack.c b/tools/testing/selftests/bpf/prog_tests/uninit_stack.c
new file mode 100644
index 000000000000..e64c71948491
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/uninit_stack.c
@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <test_progs.h>
+#include "uninit_stack.skel.h"
+
+void test_uninit_stack(void)
+{
+ RUN_TESTS(uninit_stack);
+}
diff --git a/tools/testing/selftests/bpf/progs/uninit_stack.c b/tools/testing/selftests/bpf/progs/uninit_stack.c
new file mode 100644
index 000000000000..8a403470e557
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/uninit_stack.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+/* Read an uninitialized value from stack at a fixed offset */
+SEC("socket")
+__naked int read_uninit_stack_fixed_off(void *ctx)
+{
+ asm volatile (" \
+ r0 = 0; \
+ /* force stack depth to be 128 */ \
+ *(u64*)(r10 - 128) = r1; \
+ r1 = *(u8 *)(r10 - 8 ); \
+ r0 += r1; \
+ r1 = *(u8 *)(r10 - 11); \
+ r1 = *(u8 *)(r10 - 13); \
+ r1 = *(u8 *)(r10 - 15); \
+ r1 = *(u16*)(r10 - 16); \
+ r1 = *(u32*)(r10 - 32); \
+ r1 = *(u64*)(r10 - 64); \
+ /* read from a spill of a wrong size, it is a separate \
+ * branch in check_stack_read_fixed_off() \
+ */ \
+ *(u32*)(r10 - 72) = r1; \
+ r1 = *(u64*)(r10 - 72); \
+ r0 = 0; \
+ exit; \
+"
+ ::: __clobber_all);
+}
+
+/* Read an uninitialized value from stack at a variable offset */
+SEC("socket")
+__naked int read_uninit_stack_var_off(void *ctx)
+{
+ asm volatile (" \
+ call %[bpf_get_prandom_u32]; \
+ /* force stack depth to be 64 */ \
+ *(u64*)(r10 - 64) = r0; \
+ r0 = -r0; \
+ /* give r0 a range [-31, -1] */ \
+ if r0 s<= -32 goto exit_%=; \
+ if r0 s>= 0 goto exit_%=; \
+ /* access stack using r0 */ \
+ r1 = r10; \
+ r1 += r0; \
+ r2 = *(u8*)(r1 + 0); \
+exit_%=: r0 = 0; \
+ exit; \
+"
+ :
+ : __imm(bpf_get_prandom_u32)
+ : __clobber_all);
+}
+
+static __noinline void dummy(void) {}
+
+/* Pass a pointer to uninitialized stack memory to a helper.
+ * Passed memory block should be marked as STACK_MISC after helper call.
+ */
+SEC("socket")
+__log_level(7) __msg("fp-104=mmmmmmmm")
+__naked int helper_uninit_to_misc(void *ctx)
+{
+ asm volatile (" \
+ /* force stack depth to be 128 */ \
+ *(u64*)(r10 - 128) = r1; \
+ r1 = r10; \
+ r1 += -128; \
+ r2 = 32; \
+ call %[bpf_trace_printk]; \
+ /* Call to dummy() forces print_verifier_state(..., true), \
+ * thus showing the stack state, matched by __msg(). \
+ */ \
+ call %[dummy]; \
+ r0 = 0; \
+ exit; \
+"
+ :
+ : __imm(bpf_trace_printk),
+ __imm(dummy)
+ : __clobber_all);
+}
+
+char _license[] SEC("license") = "GPL";
--
2.39.1
