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[bpf-next,2/5] selftests/bpf: Test indirect var_off stack access in raw mode

Message ID 2ede8a924105c7d26df82161d2ad2fcc5770a9ff.1554236245.git.rdna@fb.com
State Changes Requested
Delegated to: BPF Maintainers
Headers show
Series bpf: Fix indirect var_off stack access support | expand

Commit Message

Andrey Ignatov April 2, 2019, 8:19 p.m. UTC 
Test that verifier rejects indirect access to uninitialized stack with
variable offset.

Example of output:
  # ./test_verifier
  ...
  #859/p indirect variable-offset stack access, uninitialized OK

Signed-off-by: Andrey Ignatov <rdna@fb.com>
---
 .../testing/selftests/bpf/verifier/var_off.c  | 27 +++++++++++++++++++
 1 file changed, 27 insertions(+)
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/verifier/var_off.c b/tools/testing/selftests/bpf/verifier/var_off.c
index c4ebd0bb0781..7d095bd04636 100644
--- a/tools/testing/selftests/bpf/verifier/var_off.c
+++ b/tools/testing/selftests/bpf/verifier/var_off.c
@@ -114,6 +114,33 @@ 
 	.result = REJECT,
 	.prog_type = BPF_PROG_TYPE_LWT_IN,
 },
+{
+	"indirect variable-offset stack access, uninitialized",
+	.insns = {
+	BPF_MOV64_IMM(BPF_REG_2, 6),
+	BPF_MOV64_IMM(BPF_REG_3, 28),
+	/* Fill the top 16 bytes of the stack. */
+	BPF_ST_MEM(BPF_DW, BPF_REG_10, -16, 0),
+	BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
+	/* Get an unknown value. */
+	BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_1, 0),
+	/* Make it small and 4-byte aligned. */
+	BPF_ALU64_IMM(BPF_AND, BPF_REG_4, 4),
+	BPF_ALU64_IMM(BPF_SUB, BPF_REG_4, 16),
+	/* Add it to fp.  We now have either fp-12 or fp-16, we don't know
+	 * which, but either way it points to initialized stack.
+	 */
+	BPF_ALU64_REG(BPF_ADD, BPF_REG_4, BPF_REG_10),
+	BPF_MOV64_IMM(BPF_REG_5, 8),
+	/* Dereference it indirectly. */
+	BPF_EMIT_CALL(BPF_FUNC_getsockopt),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_EXIT_INSN(),
+	},
+	.errstr = "R4 invalid indirect access to uninitialized stack var_off=",
+	.result = REJECT,
+	.prog_type = BPF_PROG_TYPE_SOCK_OPS,
+},
 {
 	"indirect variable-offset stack access, ok",
 	.insns = {