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selftests/bpf: Test indirect var_off stack access in raw mode

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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>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Andrey Ignatov
2019-04-03 23:22:38 -07:00
committed by Daniel Borkmann
parent f2bcd05ec7
commit f68a5b4464
1 changed files with 27 additions and 0 deletions
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27
tools/testing/selftests/bpf/verifier/var_off.c
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@@ -114,6 +114,33 @@
.result = REJECT, .result = REJECT,
.prog_type = BPF_PROG_TYPE_LWT_IN, .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_W, 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 = "invalid indirect read from stack var_off",
.result = REJECT,
.prog_type = BPF_PROG_TYPE_SOCK_OPS,
},
{ {
"indirect variable-offset stack access, ok", "indirect variable-offset stack access, ok",
.insns = { .insns = {