xref: /kernel/linux/linux-5.10/tools/testing/selftests/bpf/verifier/var_off.c

{
	"variable-offset ctx access",
	.insns = {
	/* 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),
	/* add it to skb.  We now have either &skb->len or
	 * &skb->pkt_type, but we don't know which
	 */
	BPF_ALU64_REG(BPF_ADD, BPF_REG_1, BPF_REG_2),
	/* dereference it */
	BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1, 0),
	BPF_EXIT_INSN(),
	},
	.errstr = "variable ctx access var_off=(0x0; 0x4)",
	.result = REJECT,
	.prog_type = BPF_PROG_TYPE_LWT_IN,
},
{
	"variable-offset stack read, priv vs unpriv",
	.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, 8),
	/* add it to fp.  We now have either fp-4 or fp-8, but
	 * we don't know which
	 */
	BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_10),
	/* dereference it for a stack read */
	BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_2, 0),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_EXIT_INSN(),
	},
	.result = ACCEPT,
	.result_unpriv = REJECT,
	.errstr_unpriv = "R2 variable stack access prohibited for !root",
	.prog_type = BPF_PROG_TYPE_CGROUP_SKB,
},
{
	"variable-offset stack read, uninitialized",
	.insns = {
	/* 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, 8),
	/* add it to fp.  We now have either fp-4 or fp-8, but
	 * we don't know which
	 */
	BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_10),
	/* dereference it for a stack read */
	BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_2, 0),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_EXIT_INSN(),
	},
	.result = REJECT,
	.errstr = "invalid variable-offset read from stack R2",
	.prog_type = BPF_PROG_TYPE_LWT_IN,
},
{
	"variable-offset stack write, priv vs unpriv",
	.insns = {
	/* Get an unknown value */
	BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 0),
	/* Make it small and 8-byte aligned */
	BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 8),
	BPF_ALU64_IMM(BPF_SUB, BPF_REG_2, 16),
	/* Add it to fp.  We now have either fp-8 or fp-16, but
	 * we don't know which
	 */
	BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_10),
	/* Dereference it for a stack write */
	BPF_ST_MEM(BPF_DW, BPF_REG_2, 0, 0),
	/* Now read from the address we just wrote. This shows
	 * that, after a variable-offset write, a priviledged
	 * program can read the slots that were in the range of
	 * that write (even if the verifier doesn't actually know
	 * if the slot being read was really written to or not.
	 */
	BPF_LDX_MEM(BPF_DW, BPF_REG_3, BPF_REG_2, 0),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_EXIT_INSN(),
	},
	/* Variable stack access is rejected for unprivileged.
	 */
	.errstr_unpriv = "R2 variable stack access prohibited for !root",
	.result_unpriv = REJECT,
	.result = ACCEPT,
},
{
	"variable-offset stack write clobbers spilled regs",
	.insns = {
	/* Dummy instruction; needed because we need to patch the next one
	 * and we can't patch the first instruction.
	 */
	BPF_MOV64_IMM(BPF_REG_6, 0),
	/* Make R0 a map ptr */
	BPF_LD_MAP_FD(BPF_REG_0, 0),
	/* Get an unknown value */
	BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 0),
	/* Make it small and 8-byte aligned */
	BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 8),
	BPF_ALU64_IMM(BPF_SUB, BPF_REG_2, 16),
	/* Add it to fp. We now have either fp-8 or fp-16, but
	 * we don't know which.
	 */
	BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_10),
	/* Spill R0(map ptr) into stack */
	BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -8),
	/* Dereference the unknown value for a stack write */
	BPF_ST_MEM(BPF_DW, BPF_REG_2, 0, 0),
	/* Fill the register back into R2 */
	BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_10, -8),
	/* Try to dereference R2 for a memory load */
	BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_2, 8),
	BPF_EXIT_INSN(),
	},
	.fixup_map_hash_8b = { 1 },
	/* The unpriviledged case is not too interesting; variable
	 * stack access is rejected.
	 */
	.errstr_unpriv = "R2 variable stack access prohibited for !root",
	.result_unpriv = REJECT,
	/* In the priviledged case, dereferencing a spilled-and-then-filled
	 * register is rejected because the previous variable offset stack
	 * write might have overwritten the spilled pointer (i.e. we lose track
	 * of the spilled register when we analyze the write).
	 */
	.errstr = "R2 invalid mem access 'inv'",
	.result = REJECT,
},
{
	"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 = "invalid unbounded variable-offset indirect access to stack R4",
	.result = REJECT,
	.prog_type = BPF_PROG_TYPE_SOCK_OPS,
},
{
	"indirect variable-offset stack access, max 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, 8),
	/* add it to fp.  We now have either fp-4 or fp-8, 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 = "invalid variable-offset indirect access to stack R2",
	.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 = "invalid variable-offset indirect access to stack R2",
	.result = REJECT,
	.prog_type = BPF_PROG_TYPE_LWT_IN,
},
{
	"indirect variable-offset stack access, max_off+size > max_initialized",
	.insns = {
	/* Fill only the second from top 8 bytes of the stack. */
	BPF_ST_MEM(BPF_DW, BPF_REG_10, -16, 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, 16),
	/* Add it to fp.  We now have either fp-12 or fp-16, but we don't know
	 * which. fp-12 size 8 is partially uninitialized stack.
	 */
	BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_10),
	/* Dereference it indirectly. */
	BPF_LD_MAP_FD(BPF_REG_1, 0),
	BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_EXIT_INSN(),
	},
	.fixup_map_hash_8b = { 5 },
	.errstr = "invalid indirect read from stack R2 var_off",
	.result = REJECT,
	.prog_type = BPF_PROG_TYPE_LWT_IN,
},
{
	"indirect variable-offset stack access, min_off < min_initialized",
	.insns = {
	/* Fill only 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, 16),
	/* Add it to fp.  We now have either fp-12 or fp-16, but we don't know
	 * which. fp-16 size 8 is partially uninitialized stack.
	 */
	BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_10),
	/* Dereference it indirectly. */
	BPF_LD_MAP_FD(BPF_REG_1, 0),
	BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_EXIT_INSN(),
	},
	.fixup_map_hash_8b = { 5 },
	.errstr = "invalid indirect read from stack R2 var_off",
	.result = REJECT,
	.prog_type = BPF_PROG_TYPE_LWT_IN,
},
{
	"indirect variable-offset stack access, priv vs unpriv",
	.insns = {
	/* 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_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, 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_2, BPF_REG_10),
	/* Dereference it indirectly. */
	BPF_LD_MAP_FD(BPF_REG_1, 0),
	BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_EXIT_INSN(),
	},
	.fixup_map_hash_8b = { 6 },
	.errstr_unpriv = "R2 variable stack access prohibited for !root",
	.result_unpriv = REJECT,
	.result = ACCEPT,
	.prog_type = BPF_PROG_TYPE_CGROUP_SKB,
},
{
	"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 R4 var_off",
	.result = REJECT,
	.prog_type = BPF_PROG_TYPE_SOCK_OPS,
},
{
	"indirect variable-offset stack access, ok",
	.insns = {
	/* 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_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, 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_2, BPF_REG_10),
	/* Dereference it indirectly. */
	BPF_LD_MAP_FD(BPF_REG_1, 0),
	BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_EXIT_INSN(),
	},
	.fixup_map_hash_8b = { 6 },
	.result = ACCEPT,
	.prog_type = BPF_PROG_TYPE_LWT_IN,
},