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var_off.c
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var_off.c
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{
"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 */
BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_2, 0),
BPF_EXIT_INSN(),
},
.errstr = "variable stack access var_off=(0xfffffffffffffff8; 0x4)",
.result = REJECT,
.prog_type = BPF_PROG_TYPE_LWT_IN,
},
{
"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,
},