Commit f68a5b44 authored by Andrey Ignatov's avatar Andrey Ignatov Committed by Daniel Borkmann
Browse files

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



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: default avatarAndrey Ignatov <rdna@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent f2bcd05e

tools/testing/selftests/bpf/verifier/var_off.c

+27 −0
Original line number Diff line number Diff line
@@ -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_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",

	.insns = {

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