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selftests/bpf: Test unbounded var_off stack access

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Test the case when reg->smax_value is too small/big and can overflow,
and separately min and max values outside of stack bounds.

Example of output:
  # ./test_verifier
  #856/p indirect variable-offset stack access, unbounded OK
  #857/p indirect variable-offset stack access, max out of bound OK
  #858/p indirect variable-offset stack access, min out of bound 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 23:22:42 -07:00 committed by Daniel Borkmann
parent 107c26a70c
commit 07f9196241
1 changed files with 55 additions and 2 deletions
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57
tools/testing/selftests/bpf/verifier/var_off.c
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@ -40,7 +40,35 @@
.prog_type = BPF_PROG_TYPE_LWT_IN, .prog_type = BPF_PROG_TYPE_LWT_IN,
}, },
{ {
"indirect variable-offset stack access, out of bound", "indirect variable-offset stack access, unbounded",
.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_DW, BPF_REG_4, BPF_REG_1, offsetof(struct bpf_sock_ops,
bytes_received)),
/* Check the lower bound but don't check the upper one. */
BPF_JMP_IMM(BPF_JSLT, BPF_REG_4, 0, 4),
/* Point the lower bound to initialized stack. Offset is now in range
* from fp-16 to fp+0x7fffffffffffffef, i.e. max value is unbounded.
*/
BPF_ALU64_IMM(BPF_SUB, BPF_REG_4, 16),
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 unbounded indirect variable offset stack access",
.result = REJECT,
.prog_type = BPF_PROG_TYPE_SOCK_OPS,
},
{
"indirect variable-offset stack access, max out of bound",
.insns = { .insns = {
/* Fill the top 8 bytes of the stack */ /* Fill the top 8 bytes of the stack */
BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
@ -60,7 +88,32 @@
BPF_EXIT_INSN(), BPF_EXIT_INSN(),
}, },
.fixup_map_hash_8b = { 5 }, .fixup_map_hash_8b = { 5 },
.errstr = "invalid stack type R2 var_off", .errstr = "R2 max value is outside of stack bound",
.result = REJECT,
.prog_type = BPF_PROG_TYPE_LWT_IN,
},
{
"indirect variable-offset stack access, min out of bound",
.insns = {
/* Fill the top 8 bytes of the stack */
BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
/* Get an unknown value */
BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 0),
/* Make it small and 4-byte aligned */
BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 4),
BPF_ALU64_IMM(BPF_SUB, BPF_REG_2, 516),
/* add it to fp. We now have either fp-516 or fp-512, but
* we don't know which
*/
BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_10),
/* dereference it indirectly */
BPF_LD_MAP_FD(BPF_REG_1, 0),
BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.fixup_map_hash_8b = { 5 },
.errstr = "R2 min value is outside of stack bound",
.result = REJECT, .result = REJECT,
.prog_type = BPF_PROG_TYPE_LWT_IN, .prog_type = BPF_PROG_TYPE_LWT_IN,
}, },