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-rw-r--r--include/linux/bpf.h1
-rw-r--r--kernel/bpf/verifier.c42
2 files changed, 33 insertions, 10 deletions
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 0cadbb7456c0..51e498e5470e 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -65,6 +65,7 @@ enum bpf_arg_type {
*/
ARG_PTR_TO_STACK, /* any pointer to eBPF program stack */
ARG_CONST_STACK_SIZE, /* number of bytes accessed from stack */
+ ARG_CONST_STACK_SIZE_OR_ZERO, /* number of bytes accessed from stack or 0 */
ARG_PTR_TO_CTX, /* pointer to context */
ARG_ANYTHING, /* any (initialized) argument is ok */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 42ba4ccc020b..36dc497deaa3 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -779,15 +779,24 @@ static int check_xadd(struct verifier_env *env, struct bpf_insn *insn)
* bytes from that pointer, make sure that it's within stack boundary
* and all elements of stack are initialized
*/
-static int check_stack_boundary(struct verifier_env *env,
- int regno, int access_size)
+static int check_stack_boundary(struct verifier_env *env, int regno,
+ int access_size, bool zero_size_allowed)
{
struct verifier_state *state = &env->cur_state;
struct reg_state *regs = state->regs;
int off, i;
- if (regs[regno].type != PTR_TO_STACK)
+ if (regs[regno].type != PTR_TO_STACK) {
+ if (zero_size_allowed && access_size == 0 &&
+ regs[regno].type == CONST_IMM &&
+ regs[regno].imm == 0)
+ return 0;
+
+ verbose("R%d type=%s expected=%s\n", regno,
+ reg_type_str[regs[regno].type],
+ reg_type_str[PTR_TO_STACK]);
return -EACCES;
+ }
off = regs[regno].imm;
if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
@@ -830,15 +839,24 @@ static int check_func_arg(struct verifier_env *env, u32 regno,
return 0;
}
- if (arg_type == ARG_PTR_TO_STACK || arg_type == ARG_PTR_TO_MAP_KEY ||
+ if (arg_type == ARG_PTR_TO_MAP_KEY ||
arg_type == ARG_PTR_TO_MAP_VALUE) {
expected_type = PTR_TO_STACK;
- } else if (arg_type == ARG_CONST_STACK_SIZE) {
+ } else if (arg_type == ARG_CONST_STACK_SIZE ||
+ arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) {
expected_type = CONST_IMM;
} else if (arg_type == ARG_CONST_MAP_PTR) {
expected_type = CONST_PTR_TO_MAP;
} else if (arg_type == ARG_PTR_TO_CTX) {
expected_type = PTR_TO_CTX;
+ } else if (arg_type == ARG_PTR_TO_STACK) {
+ expected_type = PTR_TO_STACK;
+ /* One exception here. In case function allows for NULL to be
+ * passed in as argument, it's a CONST_IMM type. Final test
+ * happens during stack boundary checking.
+ */
+ if (reg->type == CONST_IMM && reg->imm == 0)
+ expected_type = CONST_IMM;
} else {
verbose("unsupported arg_type %d\n", arg_type);
return -EFAULT;
@@ -868,8 +886,8 @@ static int check_func_arg(struct verifier_env *env, u32 regno,
verbose("invalid map_ptr to access map->key\n");
return -EACCES;
}
- err = check_stack_boundary(env, regno, (*mapp)->key_size);
-
+ err = check_stack_boundary(env, regno, (*mapp)->key_size,
+ false);
} else if (arg_type == ARG_PTR_TO_MAP_VALUE) {
/* bpf_map_xxx(..., map_ptr, ..., value) call:
* check [value, value + map->value_size) validity
@@ -879,9 +897,12 @@ static int check_func_arg(struct verifier_env *env, u32 regno,
verbose("invalid map_ptr to access map->value\n");
return -EACCES;
}
- err = check_stack_boundary(env, regno, (*mapp)->value_size);
+ err = check_stack_boundary(env, regno, (*mapp)->value_size,
+ false);
+ } else if (arg_type == ARG_CONST_STACK_SIZE ||
+ arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) {
+ bool zero_size_allowed = (arg_type == ARG_CONST_STACK_SIZE_OR_ZERO);
- } else if (arg_type == ARG_CONST_STACK_SIZE) {
/* bpf_xxx(..., buf, len) call will access 'len' bytes
* from stack pointer 'buf'. Check it
* note: regno == len, regno - 1 == buf
@@ -891,7 +912,8 @@ static int check_func_arg(struct verifier_env *env, u32 regno,
verbose("ARG_CONST_STACK_SIZE cannot be first argument\n");
return -EACCES;
}
- err = check_stack_boundary(env, regno - 1, reg->imm);
+ err = check_stack_boundary(env, regno - 1, reg->imm,
+ zero_size_allowed);
}
return err;