On 8/9/22 3:45 PM, Roberto Sassu wrote:
> Allow the bpf_dynptr_kern parameter to be specified in kfuncs. Also, ensure
> that the dynamic pointer is valid and initialized.
>
> Cc: Joanne Koong <[email protected]>
> Signed-off-by: Roberto Sassu <[email protected]>
> ---
> include/linux/bpf_verifier.h | 3 +++
> kernel/bpf/btf.c | 17 +++++++++++++++++
> kernel/bpf/verifier.c | 4 ++--
> 3 files changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> index 2e3bad8640dc..55876fbdbae2 100644
> --- a/include/linux/bpf_verifier.h
> +++ b/include/linux/bpf_verifier.h
> @@ -560,6 +560,9 @@ int check_kfunc_mem_size_reg(struct bpf_verifier_env *env, struct bpf_reg_state
> u32 regno);
> int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
> u32 regno, u32 mem_size);
> +bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env,
> + struct bpf_reg_state *reg,
> + enum bpf_arg_type arg_type);
>
> /* this lives here instead of in bpf.h because it needs to dereference tgt_prog */
> static inline u64 bpf_trampoline_compute_key(const struct bpf_prog *tgt_prog,
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 67dfc728fbf8..17cca396c89f 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -6363,6 +6363,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
>
> if (is_kfunc) {
> bool arg_mem_size = i + 1 < nargs && is_kfunc_arg_mem_size(btf, &args[i + 1], ®s[regno + 1]);
> + bool arg_dynptr = btf_type_is_struct(ref_t) &&
> + !strcmp(ref_tname, "bpf_dynptr_kern");
For the strcmp(), could we add some BUILD_BUG_ON() if "bpf_dynptr_kern" ever
gets renamed? I played a bit with the below compile-tested toy example. If we
rename foo_bar into something else, we then get:
[...]
CC net/core/dev.o
In file included from <command-line>:
net/core/dev.c: In function ‘net_dev_init’:
net/core/dev.c:11376:25: error: invalid application of ‘sizeof’ to incomplete type ‘struct foo_bar’
11376 | ({ BUILD_BUG_ON(sizeof(struct x) < 0); \
| ^~~~~~
[...]
diff --git a/net/core/dev.c b/net/core/dev.c
index 716df64fcfa5..a2ed271f7ded 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -11368,16 +11368,30 @@ static struct pernet_operations __net_initdata default_device_ops = {
*
*/
+struct foo_bar {
+ int a;
+};
+
+#define stringify_struct(x) \
+ ({ BUILD_BUG_ON(sizeof(struct x) < 0); \
+ __stringify(x); })
+
/*
* This is called single threaded during boot, so no need
* to take the rtnl semaphore.
*/
static int __init net_dev_init(void)
{
+ const char *ref_tname = "abc";
int i, rc = -ENOMEM;
BUG_ON(!dev_boot_phase);
+ printk("%s\n", stringify_struct(foo_bar));
+
+ if (!strcmp(ref_tname, stringify_struct(foo_bar)))
+ goto out;
+
if (dev_proc_init())
goto out;