diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 2fe89138309a6cbc38a8507cbfbf42a1f8566119..87221fda132188fecd42fcfe1045d20ab89ca43a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2157,6 +2157,29 @@ static int check_xadd(struct bpf_verifier_env *env, int insn_idx, struct bpf_ins
BPF_SIZE(insn->code), BPF_WRITE, -1, true);
}
+static int __check_stack_boundary(struct bpf_verifier_env *env, u32 regno,
+ int off, int access_size,
+ bool zero_size_allowed)
+{
+ struct bpf_reg_state *reg = reg_state(env, regno);
+
+ if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
+ access_size < 0 || (access_size == 0 && !zero_size_allowed)) {
+ if (tnum_is_const(reg->var_off)) {
+ verbose(env, "invalid stack type R%d off=%d access_size=%d\n",
+ regno, off, access_size);
+ } else {
+ char tn_buf[48];
+
+ tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
+ verbose(env, "invalid stack type R%d var_off=%s access_size=%d\n",
+ regno, tn_buf, access_size);
+ }
+ return -EACCES;
+ }
+ return 0;
+}
+
/* when register 'regno' is passed into function that will read 'access_size'
* bytes from that pointer, make sure that it's within stack boundary
* and all elements of stack are initialized.
@@ -2169,7 +2192,7 @@ static int check_stack_boundary(struct bpf_verifier_env *env, int regno,
{
struct bpf_reg_state *reg = reg_state(env, regno);
struct bpf_func_state *state = func(env, reg);
- int off, i, slot, spi;
+ int err, min_off, max_off, i, slot, spi;
if (reg->type != PTR_TO_STACK) {
/* Allow zero-byte read from NULL, regardless of pointer type */
@@ -2183,21 +2206,23 @@ static int check_stack_boundary(struct bpf_verifier_env *env, int regno,
return -EACCES;
}
- /* Only allow fixed-offset stack reads */
- if (!tnum_is_const(reg->var_off)) {
- char tn_buf[48];
-
- tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
- verbose(env, "invalid variable stack read R%d var_off=%s\n",
- regno, tn_buf);
- return -EACCES;
- }
- off = reg->off + reg->var_off.value;
- if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
- access_size < 0 || (access_size == 0 && !zero_size_allowed)) {
- verbose(env, "invalid stack type R%d off=%d access_size=%d\n",
- regno, off, access_size);
- return -EACCES;
+ if (tnum_is_const(reg->var_off)) {
+ min_off = max_off = reg->var_off.value + reg->off;
+ err = __check_stack_boundary(env, regno, min_off, access_size,
+ zero_size_allowed);
+ if (err)
+ return err;
+ } else {
+ min_off = reg->smin_value + reg->off;
+ max_off = reg->umax_value + reg->off;
+ err = __check_stack_boundary(env, regno, min_off, access_size,
+ zero_size_allowed);
+ if (err)
+ return err;
+ err = __check_stack_boundary(env, regno, max_off, access_size,
+ zero_size_allowed);
+ if (err)
+ return err;
}
if (meta && meta->raw_mode) {
@@ -2206,10 +2231,10 @@ static int check_stack_boundary(struct bpf_verifier_env *env, int regno,
return 0;
}
- for (i = 0; i < access_size; i++) {
+ for (i = min_off; i < max_off + access_size; i++) {
u8 *stype;
- slot = -(off + i) - 1;
+ slot = -i - 1;
spi = slot / BPF_REG_SIZE;
if (state->allocated_stack <= slot)
goto err;
@@ -2222,8 +2247,16 @@ static int check_stack_boundary(struct bpf_verifier_env *env, int regno,
goto mark;
}
err:
- verbose(env, "invalid indirect read from stack off %d+%d size %d\n",
- off, i, access_size);
+ if (tnum_is_const(reg->var_off)) {
+ verbose(env, "invalid indirect read from stack off %d+%d size %d\n",
+ min_off, i - min_off, access_size);
+ } else {
+ char tn_buf[48];
+
+ tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
+ verbose(env, "invalid indirect read from stack var_off %s+%d size %d\n",
+ tn_buf, i - min_off, access_size);
+ }
return -EACCES;
mark:
/* reading any byte out of 8-byte 'spill_slot' will cause
@@ -2232,7 +2265,7 @@ static int check_stack_boundary(struct bpf_verifier_env *env, int regno,
mark_reg_read(env, &state->stack[spi].spilled_ptr,
state->stack[spi].spilled_ptr.parent);
}
- return update_stack_depth(env, state, off);
+ return update_stack_depth(env, state, min_off);
}
static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
diff --git a/tools/testing/selftests/bpf/verifier/var_off.c b/tools/testing/selftests/bpf/verifier/var_off.c
index 1e536ff121a5c0199a0316b9aec76ed1d0563313..c4ebd0bb07814f6c1095ea153b7c0bb065e19ed0 100644
--- a/tools/testing/selftests/bpf/verifier/var_off.c
+++ b/tools/testing/selftests/bpf/verifier/var_off.c
@@ -40,7 +40,7 @@
.prog_type = BPF_PROG_TYPE_LWT_IN,
},
{
- "indirect variable-offset stack access",
+ "indirect variable-offset stack access, out of bound",
.insns = {
/* Fill the top 8 bytes of the stack */
BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
@@ -60,7 +60,82 @@
BPF_EXIT_INSN(),
},
.fixup_map_hash_8b = { 5 },
- .errstr = "variable stack read R2",
+ .errstr = "invalid stack type R2 var_off",
.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 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 var_off",
+ .result = REJECT,
+ .prog_type = BPF_PROG_TYPE_LWT_IN,
+},
+{
+ "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,
+},