5.15-stable review patch. If anyone has any objections, please let me know.
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From: Daniel Borkmann daniel@iogearbox.net
commit 6788ab23508bddb0a9d88e104284922cb2c22b77 upstream.
Right now the assertion on check_ptr_off_reg() is only enforced for register types PTR_TO_CTX (and open coded also for PTR_TO_BTF_ID), however, this is insufficient since many other PTR_TO_* register types such as PTR_TO_FUNC do not handle/expect register offsets when passed to helper functions.
Given this can slip-through easily when adding new types, make this an explicit allow-list and reject all other current and future types by default if this is encountered.
Also, extend check_ptr_off_reg() to handle PTR_TO_BTF_ID as well instead of duplicating it. For PTR_TO_BTF_ID, reg->off is used for BTF to match expected BTF ids if struct offset is used. This part still needs to be allowed, but the dynamic off from the tnum must be rejected.
Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper") Fixes: eaa6bcb71ef6 ("bpf: Introduce bpf_per_cpu_ptr()") Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: John Fastabend john.fastabend@gmail.com Acked-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Edward Liaw edliaw@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/bpf/verifier.c | 39 ++++++++++++++++++++++++++++----------- 1 file changed, 28 insertions(+), 11 deletions(-)
--- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3980,14 +3980,15 @@ static int get_callee_stack_depth(struct } #endif
-int check_ptr_off_reg(struct bpf_verifier_env *env, - const struct bpf_reg_state *reg, int regno) +static int __check_ptr_off_reg(struct bpf_verifier_env *env, + const struct bpf_reg_state *reg, int regno, + bool fixed_off_ok) { /* Access to this pointer-typed register or passing it to a helper * is only allowed in its original, unmodified form. */
- if (reg->off) { + if (!fixed_off_ok && reg->off) { verbose(env, "dereference of modified %s ptr R%d off=%d disallowed\n", reg_type_str(env, reg->type), regno, reg->off); return -EACCES; @@ -4005,6 +4006,12 @@ int check_ptr_off_reg(struct bpf_verifie return 0; }
+int check_ptr_off_reg(struct bpf_verifier_env *env, + const struct bpf_reg_state *reg, int regno) +{ + return __check_ptr_off_reg(env, reg, regno, false); +} + static int __check_buffer_access(struct bpf_verifier_env *env, const char *buf_info, const struct bpf_reg_state *reg, @@ -5267,12 +5274,6 @@ found: kernel_type_name(btf_vmlinux, *arg_btf_id)); return -EACCES; } - - if (!tnum_is_const(reg->var_off) || reg->var_off.value) { - verbose(env, "R%d is a pointer to in-kernel struct with non-zero offset\n", - regno); - return -EACCES; - } }
return 0; @@ -5327,10 +5328,26 @@ static int check_func_arg(struct bpf_ver if (err) return err;
- if (type == PTR_TO_CTX) { - err = check_ptr_off_reg(env, reg, regno); + switch ((u32)type) { + case SCALAR_VALUE: + /* Pointer types where reg offset is explicitly allowed: */ + case PTR_TO_PACKET: + case PTR_TO_PACKET_META: + case PTR_TO_MAP_KEY: + case PTR_TO_MAP_VALUE: + case PTR_TO_MEM: + case PTR_TO_MEM | MEM_RDONLY: + case PTR_TO_BUF: + case PTR_TO_BUF | MEM_RDONLY: + case PTR_TO_STACK: + break; + /* All the rest must be rejected: */ + default: + err = __check_ptr_off_reg(env, reg, regno, + type == PTR_TO_BTF_ID); if (err < 0) return err; + break; }
skip_type_check: